@article{GDZPPN001252623, title = {Inverse semigroup varieties with the amalgamation property.}, journal = {Semigroup forum}, volume = {16}, year = {1978}, pages = {37-52}, zbl = {0396.20039}, url = {http://dml.mathdoc.fr/item/GDZPPN001252623} }
Hall, T.E. Inverse semigroup varieties with the amalgamation property.. Semigroup forum, Tome 16 (1978) pp. 37-52. http://gdmltest.u-ga.fr/item/GDZPPN001252623/