@article{GDZPPN001263315, title = {Solid varieties of semigroups.}, journal = {Semigroup forum}, volume = {48}, year = {1994}, pages = {219-234}, zbl = {0797.20045}, url = {http://dml.mathdoc.fr/item/GDZPPN001263315} }
Denecke, K.; Wismath, S.L. Solid varieties of semigroups.. Semigroup forum, Tome 48 (1994) pp. 219-234. http://gdmltest.u-ga.fr/item/GDZPPN001263315/