@article{SF_1992__44_1_135128,
     author = {J. Kadourek},
     title = {On varieties of combinatorial   inverse semigroups {II.}},
     journal = {Semigroup forum},
     pages = {53--78},
     year = {1992},
     volume = {44},
     number = {1},
     zbl = {0768.20024},
     url = {http://geodesic.mathdoc.fr/item/SF_1992__44_1_135128/}
}