@article{SF_1981__23_134518,
     author = {P.M. Higgins},
     title = {Epis are onto for generalized inverse semigroups.},
     journal = {Semigroup forum},
     pages = {255--260},
     year = {1981},
     volume = {23},
     zbl = {0475.20052},
     url = {http://geodesic.mathdoc.fr/item/SF_1981__23_134518/}
}