@article{GDZPPN001247832,
title = {On extensions onto sub-semigroups of semigroups with two generators.},
journal = {Semigroup forum},
volume = {2},
year = {1971},
pages = {86-88},
zbl = {0237.20061},
url = {http://dml.mathdoc.fr/item/GDZPPN001247832}
}
Hedrlin, Z.; Kastl, J. On extensions onto sub-semigroups of semigroups with two generators.. Semigroup forum, Tome 2 (1971) pp. 86-88. http://gdmltest.u-ga.fr/item/GDZPPN001247832/