@article{SF_1975__10_134094,
     author = {M.I. Klun},
     title = {A characterization of varieties of inverse semigroups.},
     journal = {Semigroup forum},
     pages = {1--7},
     year = {1975},
     volume = {10},
     zbl = {0298.20051},
     url = {http://geodesic.mathdoc.fr/item/SF_1975__10_134094/}
}