1. Ito, K., McKean, H. P., Jr.: Diffusion processes and their sample paths. Berlin-Heidelberg-New York: Springer 1965
2. Krein, M. G.: On a generalization of an investigation by Stieltjes. Dokl. Akad. Nauk 87 (6), 881?884 (1952), in Russian
3. Krein, M. G.: On some cases of the effective determination of the density of an inhomogeneous string from its spectral function. Dokl. Akad. Nauk 93 (4), 617?620 (1953), in Russian
4. Shiga, T., Watanabe, S.: Bessel diffusions as a one-parameter family of diffusion processes. Z. Wahrscheinlichkeitstheorie verw. Gebiete 27, 37?46 (1973)
5. Watanabe, S.: On one-dimensional elastic barrier Brownian motion. Sûgaku 26, 153?155 (1974), in Japanese