1. British Pharmaceutical Codex 1968, Supplement 1971, The Pharmaceutical Press, London, 1971
2. The Merck Index, 8th Ed., Merck and Co., Inc., Rahway, N.J., 1968
3. The Infra-red Spectra of Complex Molecules, 2nd Ed.;Bellamy,1958
4. G. Schilling, Ayerst Research Laboratories, personal communication