Citation: Wyckoff, R. W. G. (1935). Pages 25 & 27 from the second edition supplement of The Structure of Crystals by Wyckoff R W G. published by Reinhold Publishing Corporation, INC,Camden,N. J. in 1935 & http://cimesg1.epfl.ch/CIOLS/crystal1.pl. The second edition supplement of The Structure of Crystals, , pp. 25-27.