1. Ashton, W. D.: The theory of road traffic flow. London: Methuen 1966.
2. Croft, H. T.: A question of limits. Eureka 20, 11?13 (1957).
3. Davidson, R.: Private communication (to be published).
4. Feller, W.: On the Fourier representation for Markov chains and the strong ratio theorem. J. Math. Mech. 15, 273?283 (1966).
5. ?: An introduction to probability theory and its applications, Vol. II. New York: Wiley 1966.