1. Bednarek, A. R. and Wallace, A. D.,Equivalences on machine state spaces, Mat. Casopsis Sloven Akad. Vied., 17 (1967), 1–7.
2. Borrego, J. T. and DeVun, E. E.,Point-transitive actions by the unit interval, Canadian J. Math. 22 (1970), 255–259.
3. Hofmann, K. H. and Mostert, P. S.,Elements of compact semigroups, C. E. Merrill Books, Columbus, Ohio (1966).
4. Paalman-de Miranda, A. B.,Topological semigroups, Mathematical Center, Amsterdam (1964).
5. Stadtlander, D. P.,Thread actions, Duke Math. J. 35 (1968), 483–490.