1. M. Kac, Probability and Related Topics in Physical Sciences, London (1959).
2. R. Høegh-Krohn, Commun. Math. Phys.,38, 195 (1974).
3. V. V. Borzov, Matem. Zametki,26, 547 (1979).
4. E. Nelson, J. Funct. Anal.,12, 211 (1973).
5. B. Simon, The P(?)2 Euclidean Quantum Field Theory, Princeton, New Jersey (1974).