1. Callaway, D.J.E., Cooper, F., Klauder, J.R., and Rose, H.A., 1985, Nucl. Phys. B 262, 19
2. Chan, H.S., and Halpern, M.B., 1987, Zeitschr. Phys. C 39, 669
3. DeWitt, B.S., 1962, J. Math. Phys. 3, 1073
4. DeWitt, B.S., 1965, “Dynamical Theory of Groups and Fields”, Gordon and Breach, New York
5. Fradkin, E.S., and Vilkovisky, G.A., 1973, Phys. Rev. D 8, 4241