1. McKenna E., Koch W.J., Slish D.F. and Schwartz A., Biochem. Pharmacol., 39 (1990) 1145.
2. Fleckenstein-Grun G., Frey M. and Fleckenstein A., Trends Pharmacol. Sci., 7 (1984) 283.
3. Nayler W.G., Z. Kardiol. 79, suppl. 3 (1990) 107.
4. Mannhold R., Bayer R., Ronsdorf M. and Martens L., Arzneim. Forsch./Drug Res., 37 (1987) 419.
5. Mannhold R., In Melchiorre C. and Giannella M. (Eds.) Recent Advances in Receptor Chemistry, Elsevier, Amsterdam, 1988, p. 147, and references cited therein.