1. E. Fischer: Chem.Ber. 27, 298 S (1894)
2. W.E. Purcell, G.E. Bass, J.M. Clayton: “Strategy of Drug Design, A Guide to Biological Activity”. New York; Wiley 1973
3. W.E. Purcell, In: “Biological Activity and Chemical Structure” pg.282. Jane A. Keverling-Buisman, (ed.), Elsevier Sci.Publ. 1977
4. A. Verloop, J.Tipker, ibid. p.63
5. C. Hansch, ibid p. 47