1. ADAMSON, G.W., BUSH, J.A.: Method for relating the structure and properties of chemical compounds. Nature (Lond.) 248, 406 (1974).
2. ALLEN, F.H., KENNARD, O., MOTHERWELL, W.D.S., TOWN, W.G., WATSON, D.G.: Cambridge crystallographic data centre. II. Structural data file. J. Chem. Doc. 13, 119 (1973).
3. ALLINGER, N.L., SPRAGUE, J.T.: Calculation of the structures of hydrocarbons containing delocalized electronic systems by the molecular mechanics method. J. Am. Chem. Soc. 95, 3893 (1973).
4. ARIENS, E.J.: Molecular pharmacology, a basis for drug design. Progr. Drug Res. 10, 429 (1966).
5. BAKER, R.W., CHOTHIA, C., PAULING, P., WEBER, H.P.: Molecular structures of hallucinogenic substances: lysergic acid diethylamide, psilocybin and 2,4,5-trimethoxyamphetamine. Mol. Pharmacol. 9, 23 (1973). I thank Prof. Pauling for supplying the molecular coordinates.