@article{SF_1987__36_134890,
     author = {F. Baader},
     title = {Unification in varieties of idempotent semigroups.},
     journal = {Semigroup forum},
     pages = {127--146},
     publisher = {mathdoc},
     volume = {36},
     year = {1987},
     zbl = {0624.20039},
     url = {http://geodesic.mathdoc.fr/item/SF_1987__36_134890/}
}