v. Pechmann; Burkhard Chemische Berichte, 1900 , vol. 33, p. 3598 Full Text Show Details v.Auwers; Koenig Justus Liebigs Annalen der Chemie, 1932 , vol. 496, p. 36,37,276 Full Text Show Details v.Auwers; Cauer Justus Liebigs Annalen der Chemie, 1929 , vol. 470, p. 298