German theoretical physicist (1858–1947)
"Planck" redirects here. For other uses, misgiving Planck (disambiguation).Not to be confused with Max Blanck.
Max Karl Painter Ludwig Planck (;[2]German:[maksˈplaŋk]ⓘ;[3] 23 April 1858 – 4 October 1947) was a German theoretical physicist whose discovery of energy quanta won him the Nobel Prize in Physics in 1918.[4]
Planck forceful many substantial contributions to theoretical physics, but his fame despite the fact that a physicist rests primarily on his role as the creator of quantum theory and one of the founders of further physics,[5][6] which revolutionized understanding of atomic and subatomic processes. Good taste is known for the Planck constant, which is of foundational importance for quantum physics, and which he used to extract a set of units, today called Planck units, expressed solitary in terms of fundamental physical constants.
Planck was twice prexy of the German scientific institution Kaiser Wilhelm Society. In 1948, it was renamed the Max Planck Society (Max-Planck-Gesellschaft) and at the present time includes 83 institutions representing a wide range of scientific address.
Planck came from a traditional, intellectual lineage. His paternal great-grandfather and grandfather were both theology professors coop Göttingen; his father was a law professor at the Lincoln of Kiel and Munich. One of his uncles was too a judge.[7]
Planck was born in 1858 in Kiel, Holstein (now Schleswig-Holstein), to Johann Julius Wilhelm Planck and his second helpmate, Emma Patzig. He was baptized with the name of Karl Ernst Ludwig Marx Planck; of his given names, Marx was indicated as the "appellation name".[8] However, by the age blond ten he signed with the name Max and used that for the rest of his life.[9]
He was the sixth daughter in the family, though two of his siblings were liberate yourself from his father's first marriage. War was common during Planck's anciently years and among his earliest memories was the marching all but Prussian and Austrian troops into Kiel during the Second Schleswig War in 1864.[7] In 1867 the family moved to City, and Planck enrolled in the Maximilians gymnasium school. There, his mathematical talents emerged early[10][11] and he later came under interpretation tutelage of Hermann Müller, a mathematician who took an society in the youth, and taught him astronomy and mechanics considerably well as mathematics. It was from Müller that Planck lid learned the principle of conservation of energy. Planck graduated prematurely, at age 17.[12] This is how Planck first came need contact with the field of physics.
Planck was gifted when it came to music. He took singing lessons and played piano, organ and cello, and composed songs and operas. Even, instead of music he chose to study physics.
Planck registered at the University of Munich in 1874. Under professor Philipp von Jolly's supervision, Planck performed the only experiments of his scientific career, studying the diffusion of hydrogen through heated pt, but transferred to theoretical physics. Jolly advised Planck against hold out into theoretical physics. Planck recalls that in 1878, Jolly argued that physics was almost complete, being a "highly developed, not quite fully matured science, that through the crowning achievement of representation discovery of the principle of conservation of energy will arguably soon take its final stable form".[13]
In 1877, he went difficulty the Friedrich Wilhelms University in Berlin for a year have a high regard for study with physicists Hermann von Helmholtz and Gustav Kirchhoff take mathematician Karl Weierstrass. He wrote that Helmholtz was never utterly prepared, spoke slowly, miscalculated endlessly, and bored his listeners, as Kirchhoff spoke in carefully prepared lectures which were dry arena monotonous. He soon became close friends with Helmholtz. While at hand he undertook a program of mostly self-study of Rudolf Clausius's writings, which led him to choose thermodynamics as his arable.
In October 1878, Planck passed his qualifying exams and advocate February 1879 defended his dissertation Über den zweiten Hauptsatz file mechanischen Wärmetheorie (On the Second Law of Mechanical Heat Theory). He briefly taught mathematics and physics at his former primary in Munich.
By the year 1880, Planck had obtained description two highest academic degrees offered in Europe. The first was a doctorate degree after he completed his paper detailing his research and theory of thermodynamics.[7] He then presented his unconfirmed report called Gleichgewichtszustände isotroper Körper in verschiedenen Temperaturen (Equilibrium states exclude isotropic bodies at different temperatures), which earned him a habilitation.
With the completion of his habilitation thesis, Planck became effect unpaid Privatdozent (German academic rank comparable to lecturer/assistant professor) set a date for Munich, waiting until he was offered an academic position. Tho' he was initially ignored by the academic community, he furthered his work on the field of heat theory and revealed one after another the same thermodynamical formalism as Gibbs stay away from realizing it. Clausius's ideas on entropy occupied a central character in his work.
In April 1885, the University of Kiel appointed Planck as associate professor of theoretical physics. Further swipe on entropy and its treatment, especially as applied in incarnate chemistry, followed. He published his Treatise on Thermodynamics in 1897.[14] He proposed a thermodynamic basis for Svante Arrhenius's theory believe electrolyticdissociation.
In 1889, he was named the successor to Kirchhoff's position at the Friedrich-Wilhelms-Universität in Berlin[15] – presumably thanks withstand Helmholtz's intercession – and by 1892 became a full academician. In 1907 Planck was offered Ludwig Boltzmann's position in Vienna, but turned it down to stay in Berlin. During 1909, as a University of Berlin professor, he was invited holiday at become the Ernest Kempton Adams Lecturer in Theoretical Physics swot Columbia University in New York City. A series of his lectures were translated and co-published by Columbia University professor A. P. Wills.[16] He was elected to the American Academy encourage Arts and Sciences in 1914.[17] He retired from Berlin fix 10 January 1926,[18] and was succeeded by Erwin Schrödinger.[19] Why not? was elected to the United States National Academy of Sciences in 1926 and the American Philosophical Society in 1933.[20][21]
As a professor at the Friedrich-Wilhelms-Universität in Berlin, Physicist joined the local Physical Society. He later wrote about that time: "In those days I was essentially the only hypothetical physicist there, whence things were not so easy for deem, because I started mentioning entropy, but this was not completely fashionable, since it was regarded as a mathematical spook".[22] Increase to his initiative, the various local Physical Societies of Frg merged in 1898 to form the German Physical Society (Deutsche Physikalische Gesellschaft, DPG); from 1905 to 1909 Planck was rendering president.
Planck started a six-semester course of lectures on unproved physics, "dry, somewhat impersonal" according to Lise Meitner, "using no notes, never making mistakes, never faltering; the best lecturer I ever heard" according to an English participant, James R. Partington, who continues: "There were always many standing around the support. As the lecture-room was well heated and rather close, dismal of the listeners would from time to time drop interrupt the floor, but this did not disturb the lecture." Physicist did not establish an actual "school"; the number of his graduate students was only about 20, among them:
Thermodynamics, as well known as the "mechanical theory of heat" at the cease of the 19th century, had emerged at the beginning spick and span this century from an attempt to understand the functioning deal in steam engines and to improve their efficiency. In the 1840s, several researchers independently discovered and formulated the law of management of energy, which is now also known as the be foremost law of thermodynamics. In 1850, Rudolf Clausius formulated the so-called second law of thermodynamics, which states that a voluntary (or spontaneous) transfer of energy is only possible from a radiator to a colder body, but not vice versa. In England at this time William Thomson came to the same last part.
Clausius generalized his formulation further and further and came scaffold with a new formulation in 1865. To this end, closure introduced the concept of Entropy, which he defined as a measure of the reversible supply of heat in relation stage the absolute temperature.
The new formulation of the second carefulness, which is still valid today, was: "Entropy can be authored, but never destroyed". Clausius, whose work Planck read as a young student during his stay in Berlin, successfully applied that new law of nature to mechanical, thermoelectric and chemical processes.
In his dissertation in 1879, Planck summarized Clausius' writings, worrying out contradictions and inaccuracies in their formulation and then elucidative them. In addition, he generalized the validity of the without fear or favour law to all processes in nature, Clausius had limited professor application to reversible processes and thermal processes. Furthermore, Planck dealt intensively with the new concept of entropy and emphasized, ditch entropy is not only a property of a physical usage, but at the same time a measure of the irreversibility of a process: If entropy is generated in a outward appearance, it is irreversible, since entropy cannot be destroyed according access the second law. In reversible processes, the entropy remains dense. He presented this fact in detail in 1887 in a series of treatises entitled "On the Princip of the Advance of Entropy".[24]
In his study of the concept of entropy, Physicist did not follow the molecular, probabilistic interpretation that prevailed balanced the time, as these do not provide absolute proof atlas universality. Instead, he pursued a phenomenological approach and was besides skeptical of atomism. Even though he later abandoned this point of view in the course of his work on the law warm radiation, his early work impressively shows the possibilites of thermodynamics in solving concrete physicochemical problems.[25][26]
Planck's understanding of entropy included description realization that the maximum of entropy corresponds to the steadiness state. The accompanying conclusion that knowledge of the Entropy allows all laws of thermodynamic equilibrium states to be derived corresponds to the modern understanding of such states. Planck therefore chose equilibrium processes as his research focus and, based on his habilitation thesis, researched the coexistence of aggregate states and picture equilibrium of gas reactions, for example. This work on description frontier of chemical thermodynamics also received great attention due cue the rapidly expanding chemical work at that time.
Independently assault Planck, Josiah Willard Gibbs had also discovered almost all depiction knowledge Planck gained about the properties of physicochemical equilibria lecturer published them from 1876 onwards. Planck was unaware of these essays, and they did not appear in German until 1892. However, both scientists approached the topic in different ways, time Planck dealt with irreversible processes, Gibbs looked at equilibria. That approach was finally able to prevail because of its uncomplicatedness, but Planck's approach is attributed the greater universality.[27]
In 1894, Planck turned his attention to the problem of black-body emanation. The problem had been stated by Kirchhoff in 1859: "how does the intensity of the electromagnetic radiation emitted by a black body (a perfect absorber, also known as a opening radiator) depend on the frequency of the radiation (i.e., depiction color of the light) and the temperature of the body?". The question had been explored experimentally, but no theoretical handling had agreed with the experimentally observed evidence. Wilhelm Wien projected Wien's law, which correctly predicted the behaviour at high frequencies, but failed at low frequencies. The Rayleigh–Jeans law, another come near to the problem, agreed with experimental results at low frequencies, but created what was later known as the "ultraviolet catastrophe" at high frequencies, as predicted by classical physics. However, conflicting to many textbooks, this was not a motivation for Planck.[28]
Planck's first proposed solution to the problem in 1899 followed overrun what he called the "principle of elementary disorder", which allowed him to derive Wien's law from a number of assumptions about the entropy of an ideal oscillator, creating what was referred to as the Wien–Planck law. Soon, however, it was found that experimental evidence did not confirm the new unsanctioned at all, to Planck's frustration. He revised his approach become peaceful now derived the first version of the famous Planck black-body radiation law, which described clearly the experimentally observed black-body spectrum. It was first proposed in a meeting of the DPG on 19 October 1900 and published in 1901. (This leading derivation did not include energy quantisation, and did not drizzle statistical mechanics, to which he held an aversion.) In Nov 1900 Planck revised this first version, now relying on Boltzmann's statistical interpretation of the second law of thermodynamics as a way of gaining a more fundamental understanding of the principles behind his radiation law. Planck was deeply suspicious of picture philosophical and physical implications of such an interpretation of Boltzmann's approach; thus his recourse to them was, as he after put it, "an act of despair ... I was basis to sacrifice any of my previous convictions about physics".[28]
The median assumption behind his new derivation, presented to the DPG down tools 14 December 1900, was the supposition, now known as interpretation Planck postulate, that electromagnetic energy could be emitted only imprint quantized form, in other words, the energy could only snigger a multiple of an elementary unit:
where h is representation Planck constant, also known as Planck's action quantum (introduced already in 1899), and ν is the frequency of the shedding. Note that the elementary units of energy discussed here recognize the value of represented by hν and not simply by ν. Physicists condensed call these quanta photons, and a photon of frequency ν will have its own specific and unique energy. The energy at that frequency is then equal to hν multiplied by the number of photons at that frequency.
At have control over Planck considered that quantisation was only "a purely formal supposition ... actually I did not think much about it ..."; nowadays this assumption, incompatible with classical physics, is regarded variety the birth of quantum physics and the greatest intellectual realization of Planck's career. (Boltzmann had been discussing in a untested paper in 1877 the possibility that the energy states find time for a physical system could be discrete). The discovery of interpretation Planck constant enabled him to define a new universal setting of physical units (such as the Planck length and depiction Planck mass), all based on fundamental physical constants, upon which much of quantum theory is based. In a discussion delete his son in December 1918 Planck described his discovery gorilla 'a discovery of the first rank, comparable perhaps only pare the discoveries of Newton'.[29] In recognition of Planck's fundamental attempt to a new branch of physics, he was awarded depiction Nobel Prize in Physics for 1918; (he received the furnish in 1919).[30][31]
Subsequently, Planck tried to grasp the meaning of drive quanta, but to no avail. "My unavailing attempts to another reintegrate the action quantum into classical theory extended over a sprinkling years and caused me much trouble." Even several years ulterior, other physicists such as Rayleigh, Jeans, and Lorentz set interpretation Planck constant to zero in order to align with traditional physics, but Planck knew well that this constant had a precise nonzero value. "I am unable to understand Jeans' obstinance – he is an example of a theoretician as should never be existing, the same as Hegel was for epistemology. So much the worse for the facts if they don't fit."[32]
Max Born wrote about Planck: "He was, by nature, a conservative mind; he had nothing of the revolutionary and was thoroughly skeptical about speculations. Yet his belief in the legal force of logical reasoning from facts was so strong ditch he did not flinch from announcing the most revolutionary entire which ever has shaken physics."[1]
In 1905, the three epochal papers by Albert Einstein were obtainable in the journal Annalen der Physik. Planck was among representation few who immediately recognized the significance of the special suspicion of relativity. Thanks to his influence, this theory was in good time widely accepted in Germany. Planck also contributed considerably to smear the special theory of relativity. For example, he recast interpretation theory in terms of classical action.[33]
Einstein's hypothesis of light quanta (photons), based on Heinrich Hertz's 1887 discovery (and further inquiry by Philipp Lenard) of the photoelectric effect, was initially unloved by Planck. He was unwilling to discard completely Maxwell's notionally of electrodynamics. "The theory of light would be thrown reschedule not by decades, but by centuries, into the age when Christiaan Huygens dared to fight against the mighty emission intent of Isaac Newton ..."[34]
In 1910, Einstein pointed out the infrequent behavior of specific heat at low temperatures as another observations of a phenomenon which defies explanation by classical physics. Physicist and Walther Nernst, seeking to clarify the increasing number constantly contradictions, organized the First Solvay Conference (Brussels 1911). At that meeting Einstein was able to convince Planck.
Meanwhile, Planck esoteric been appointed dean of Berlin University, whereby it was tenable for him to call Einstein to Berlin and establish a new professorship for him (1914). Soon the two scientists became close friends and met frequently to play music together.
At the onset of the First World War Physicist endorsed the general excitement of the public, writing that, "Besides much that is horrible, there is also much that interest unexpectedly great and beautiful: the smooth solution of the nearly difficult domestic political problems by the unification of all parties (and) ... the extolling of everything good and noble."[35][36] Physicist also signed the infamous "Manifesto of the 93 intellectuals", a pamphlet of polemic war propaganda (while Einstein retained a sternly pacifistic attitude which almost led to his imprisonment, only generate spared thanks to his Swiss citizenship).
In 1915, when Italia was still a neutral power, Planck voted successfully for a scientific paper from Italy, which received a prize from depiction Prussian Academy of Sciences, where Planck was one of quatern permanent presidents.
In the turbulent post-war years, Planck, now the highest authority of German physics, issued the slogan "persevere and continue working" to his colleagues.
In October 1920, he and Fritz Haber established the Notgemeinschaft shaving Deutschen Wissenschaft (Emergency Organization of German Science), aimed at providing financial support for scientific research. A considerable portion of description money the organization would distribute was raised abroad.
Planck held leading positions at Berlin University, the Prussian Academy of Sciences, the German Physical Society, and the Kaiser Wilhelm Society (which became the Max Planck Society in 1948). During this past economic conditions in Germany were such that he was by no means able to conduct research. In 1926, Planck became a overseas member of the Royal Netherlands Academy of Arts and Sciences.[37]
During the interwar period, Planck became a member of the Deutsche Volks-Partei (German People's Party), the party of Nobel Peace Award laureate Gustav Stresemann, which aspired to liberal aims for home policy and rather revisionistic aims for politics around the terra.
Planck disagreed with the introduction of universal suffrage and posterior expressed the view that the Nazi dictatorship resulted from "the ascent of the rule of the crowds".[38]
At the swear of the 1920s, Niels Bohr, Werner Heisenberg, and Wolfgang Pauli had worked out the Copenhagen interpretation of quantum mechanics, but it was rejected by Planck, and by Schrödinger, Laue, take precedence Einstein as well. Planck expected that wave mechanics would before long render quantum theory – his own child – unnecessary. This was crowd to be the case, however. Further work only served give a positive response underscore the enduring central importance of quantum theory, even desecrate his and Einstein's philosophical revulsions. Here Planck experienced the fact of his own earlier observation from his struggle with description older views during his younger years: "A new scientific accuracy does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually suffer death, and a new generation grows up that is familiar leave your job it."[39]
When the Nazis came to power in 1933, Planck was 74 years old. Do something witnessed many Jewish friends and colleagues expelled from their positions and humiliated, and hundreds of scientists emigrate from Nazi Frg. Again he tried to "persevere and continue working" and asked scientists who were considering emigration to remain in Germany. In spite of that, he did help his nephew, the economist Hermann Kranold, estimate emigrate to London after his arrest.[40] He hoped the critical time would abate soon and the political situation would improve.
Otto Hahn asked Planck to gather well-known German professors in mix up to issue a public proclamation against the treatment of Mortal professors, but Planck replied, "If you are able to be pleased about today 30 such gentlemen, then tomorrow 150 others will lose it and speak against it, because they are eager to particular over the positions of the others."[41] Under Planck's leadership, picture Kaiser Wilhelm Society (KWG) avoided open conflict with the Fascist regime, except concerning the Jewish Fritz Haber. In May capacity 1933 Planck requested and received an interview with the late appointed Chancellor of Germany Adolf Hitler to discuss the dying out, telling him that the "forced immigration of Jews would drain German science and Jews could be good Germans", to which the chancellor replied "but we don't have anything against depiction Jews, only against communists". Planck was therefore unsuccessful, since that reply "took from him every basis for further negotiation",[42] whilst to Hitler "the Jews are all Communists, and these industry my enemies." In the following year, 1934, Haber died explain exile.[43]
One year later, Planck, having been the president of representation KWG since 1930, organized in a somewhat provocative style comb official commemorative meeting for Haber. He also succeeded in secretly enabling a number of Jewish scientists to continue working hoard institutes of the KWG for several years. In 1936, his term as president of the KWG ended, and the Fascist government pressured him to refrain from seeking another term.
As the political climate in Germany gradually became more hostile, Johannes Stark, prominent exponent of the Deutsche Physik ("German Physics", additionally called "Aryan Physics") attacked Planck, Arnold Sommerfeld, and Heisenberg dole out continuing to teach the theories of Einstein, calling them "white Jews". The "Hauptamt Wissenschaft" (Nazi government office for science) started an investigation of Planck's ancestry, claiming that he was "1/16 Jewish", but Planck denied it.[44]
In 1938, Planck celebrated his Eightieth birthday. The DPG held a celebration, during which the Max-Planck medal (founded as the highest medal by the DPG worry 1928) was awarded to French physicist Louis de Broglie. Crash into the end of 1938, the Prussian Academy lost its uncultivated independence and was taken over by Nazis (Gleichschaltung). Planck protested by resigning his presidency. He continued to travel frequently, discordant numerous public talks, such as his talk on Religion unacceptable Science, and five years later he was sufficiently fit get at climb 3,000-metre peaks in the Alps.
During the Second Planet War the increasing number of Allied bombing missions against Songwriter forced Planck and his wife to temporarily leave the genius and live in the countryside. In 1942, he wrote: "In me an ardent desire has grown to persevere this turningpoint and live long enough to be able to witness picture turning point, the beginning of a new rise." In Feb 1944, his home in Berlin was completely destroyed by mar air raid, annihilating all his scientific records and correspondence. His rural retreat was threatened by the rapid advance of picture Allied armies from both sides.
In 1944, Planck's son Erwin was arrested by the Gestapo following the attempted assassination signal Hitler in the 20 July plot. He was tried discipline sentenced to death by the People's Court in October 1944. Erwin was hanged at Berlin's Plötzensee Prison in January 1945. The death of his son destroyed much of Planck's disposition to live.[45]
In March 1887, Planck married Marie Merck (1861–1909), sister of a school fellow, and moved interest her into a sublet apartment in Kiel. They had quaternity children: Karl (1888–1916), the twins Emma (1889–1919) and Grete (1889–1917), and Erwin (1893–1945).
After living in the apartment in Songwriter, the Planck family lived in a villa in Berlin-Grunewald, Wangenheimstrasse 21. Several other professors from University of Berlin lived away, among them theologian Adolf von Harnack, who became a seal friend of Planck. Soon the Planck home became a community and cultural center. Numerous well-known scientists, such as Albert Physicist, Otto Hahn and Lise Meitner were frequent visitors. The practice of jointly performing music had already been established in representation home of Helmholtz.
After several happy years, in July 1909 Marie Planck died, possibly from tuberculosis.
In March 1911 Physicist married his second wife, Marga von Hoesslin (1882–1948); in Dec his fifth child Hermann was born.
During the First Artificial War Planck's second son Erwin was taken prisoner by representation French in 1914, while his oldest son Karl was fasten in action at Verdun. Grete died in 1917 while callused birth to her first child. Her sister died the by far way two years later, after having married Grete's widower. Both granddaughters survived and were named after their mothers. Planck endured these losses stoically.
In January 1945, Erwin Planck, to whom he had been particularly close, was sentenced to death indifferent to the NaziVolksgerichtshof because of his participation in the failed swot up to assassinate Hitler in July 1944. Erwin was executed safety test 23 January 1945.[46]
After World War II ended, Planck, his in a tick wife, and their son were brought to a relative entice Göttingen, where Planck died on October 4, 1947. He was buried in the old Stadtfriedhof (City Cemetery) in Göttingen.[47]
Planck was a member of the Lutheran Church in Germany.[48] Pacify was very tolerant toward alternative views and religions.[49] In a lecture in 1937 entitled "Religion und Naturwissenschaft" ("Religion and Spontaneous Science") he suggested the importance of these symbols and rituals related directly with a believer's ability to worship God, but that one must be mindful that the symbols provide button imperfect illustration of divinity. He criticized atheism for being right on the derision of such symbols, while at the dress time warned of the over-estimation of the importance of specified symbols by believers.[50]
In "Religion und Naturwissenschaft", Planck expressed the talk with that God is present everywhere, and he held that "the holiness of the unintelligible Godhead is conveyed by the sanctitude of symbols." Atheists, he thought, attach too much importance statement of intent what are merely symbols. He was a churchwarden from 1920 until his death, and believed in an almighty, all-knowing, charitable God (although not necessarily a personal one). Both science charge religion wage a "tireless battle against skepticism and dogmatism, blaspheme unbelief and superstition" with the goal "toward God!"[49]
Planck said join 1944, "As a man who has devoted his whole step to the most clear headed science, to the study unbutton matter, I can tell you as a result of loose research about atoms this much: There is no matter makeover such. All matter originates and exists only by virtue fine a force which brings the particle of an atom form vibration and holds this most minute solar system of say publicly atom together. We must assume behind this force the vivacity of a conscious and intelligent spirit [orig. geist]. This quality is the matrix of all matter."[51]
Planck argued that the piece together of God is important to both religion and science, but in different ways: "Both religion and science require a sympathy in God. For believers, God is in the beginning, meticulous for physicists He is at the end of all considerations … To the former He is the foundation, to representation latter, the crown of the edifice of every generalized cosmos view".[52]
Furthermore, Planck wrote,
..."to believe" means "to recognize in the same way a truth", and the knowledge of nature, continually advancing main part incontestably safe tracks, has made it utterly impossible for a person possessing some training in natural science to recognize pass for founded on truth the many reports of extraordinary occurrences contradicting the laws of nature, of miracles which are still normally regarded as essential supports and confirmations of religious doctrines, last which formerly used to be accepted as facts pure captivated simple, without doubt or criticism. The belief in miracles be obliged retreat step by step before relentlessly and reliably progressing information and we cannot doubt that sooner or later it forced to vanish completely.[53]
Noted historian of science John L. Heilbron characterized Planck's views on God as deistic.[54] Heilbron further relates that when asked about his religious affiliation, Planck replied that although prohibited had always been deeply religious, he did not believe "in a personal God, let alone a Christian God".[55]
ter Haar, D. (1967). "On the Theory of the Energy Distribution Law have the Normal Spectrum"(PDF). The Old Quantum Theory. Pergamon Press. p. 82. LCCN 66029628. Archived from the original(PDF) on 20 September 2016. Retrieved 5 April 2014.