1. H. Primas and U. Müller-Herold, “Elementare Quantenchemie”, Teubner, Stuttgart (1984).
2. J.-M. Lévy-Leblond, Commun. Math. Phys. 6:286 (1967).
3. J.C.A. Boeyens, J. Chem. Ed. 72:412 (1995).
4. J.C.A. Boeyens, Electronic J. Theor. Chem. (1995), in press.
5. J.C.A. Boeyens, Gauge chemistry, in: “Large-Scale Molecular Systems: Quantum and Stochastic Aspects”, W. Gans, A. Blumen and A. Amann, (eds) Nato ASI Series B258, Plenum, New York (1991).