1. Walden P (1908) Chemik. Zeitung 32: 1053
2. Burkert U, Allinger NL (1982) Molecular mechanics, ACS monograph no. 177. Amer. Chem. Soc, Washington
3. Frühbeis H, Klein R, Wallmeier H (1987) Angew. Chem. Intl. Ed. 26: 403
4. Westheimer H (1956) in: Newman MS (ed) Steric effects in organic chemistry. Wiley, New York p 524
5. Daudel R (1988) J. Mol. Struct. 165 (3/4): xiii