1. K. L. Chung and P. Hsu: Gauge theorem for the Neumann problem, Seminar on Stochastic processes, 1984, pp. 63–70. Birkhauser, Boston, 1986.
2. N. Falkner: Feynman — Kac junctionals and positive solutions of 1/2Au + qu = 0, Zeit. Wahr. 65 (1983) 19–33.
3. P. Hsu: Probabilistic approach to the Neumann problem, Comm. Pure Appl. Math. 38 (1985) 445–472.
4. S. Ito: Fundamental solutions of parabolic differential equations and boundary value problems, Japan J. Math. 27 (1957) 55–102.
5. Z. Ma: On the probabilistic approach to boundary value problems, BiBoS 288, 1987.