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@article{SF_1977__14_186378, author = {J. A. Gerhard}, title = {Semigroups with idempotent powers, {II:} {The} lattices of equational subclasses of [(xy2 =xy] .}, journal = {Semigroup forum}, pages = {375--388}, publisher = {mathdoc}, volume = {14}, year = {1977}, zbl = {0373.20052}, url = {http://geodesic.mathdoc.fr/item/SF_1977__14_186378/} }
J. A. Gerhard. Semigroups with idempotent powers, II: The lattices of equational subclasses of [(xy2 =xy] .. Semigroup forum, Tome 14 (1977), pp. 375-388. http://geodesic.mathdoc.fr/item/SF_1977__14_186378/