[4] J. G. Bergman:
A duality theorem for standard threads. Czech. Math. J. 21(1971), 167-171.
MR 0285656 |
Zbl 0228.22007
[7] A. H. Clifford:
Connected ordered topological semigroups with idempotent end points I. T.A.M.S., 88 (1958), 80-98.
MR 0095221