[1] J. ADÁMEK V. KOUBEK:
On representations of ordered commutative semigroups. Colloquia Math. Soc. J. Bolyai 20 (1976), 15-31.
MR 0541106
[2] P. J. HILTON S. WYLIE:
Homology theory. An introduction to algebraic topology. Cambridge University Press (1960).
MR 0115161
[3] V. TRNKOVÁ:
On a representation of commutative semigroups. Semigroup Forum 10 (1975), 203-214.
MR 0374312
[4] V. TRNKOVÁ:
Isomorphism of products and representation of commutative semigroups. Colloquia Math. Soc. J. Bolyai 20 (1976), 657-683.
MR 0541143