Physicist Max Planck authored the quantum theory.

From the guide to the Max Planck correspondence, 1919-1948, 1919-1948, (American Philosophical Society)

German physicist.

From the description of Autograph letter signed : Berlin-Grunewald, to Artur Neuberg, 1939 Nov. 10. (Unknown). WorldCat record id: 270872119

Max Planck was a physicist and the author of the quantum theory. Received Nobel prize in Physics (1918). Involvement with the Kaiser-Wilhelm Society: Senator (1916-1937); Second "Schriftfuhrer" (1925-1930); President (1930-1937); Honorary senator (1937), President (1945-1946); afterwards honorary president. Society was named after him: Max-Planck Society in the Biritsh occpuation zone.

From the description of Additions to the Max Planck Collection. (Unknown). WorldCat record id: 78343015

Max Planck was a physicist and the author of the quantum theory.

From the description of Correspondence, 1919-1948. (American Philosophical Society Library). WorldCat record id: 122474083

Physicist and historian of science Thomas Darlington Cope received his A.B. (1903) and Ph.D. (1915) from the University of Pennsylvania; he became an instructor and later professor there from 1906-1952. He also studied at the University of Berlin (1912-1913) under Max Planck.

From the guide to the Thomas Darlington Cope papers, ca. 1909-1964, Circa 1909-1964, (American Philosophical Society)