Crum Brown-Gibson Rule

A. Crum Brown and J. Gibson, J. Chem. Soc. 61, 367 (1892)
H. E. Armstrong, J. Chem. Soc. 51, 258 (1887)
D. Vorlander, Ann. 320, 122 (1902)
C. K. Ingold in H. E. Rodd, Chernistry of Carbon Compounds IIIA, p 20 (New York, 1957)