Citation: Wyckoff, R. W. G. (1935). Page 54 from the second edition supplement of The Structure of Crystals by Wyckoff R W G. published by Reinhold PublishingCorporation, INC, Camden,N. J. in 1935 & http://www.crystallography.net/. The second edition supplement of The Structure of Crystals, , pp. 54-54.