@article{SF_1974__9_134080,
     author = {D.E. Zitarelli},
     title = {Compatible extensions and subdirectly irreducible inverse semigroups.},
     journal = {Semigroup forum},
     pages = {241--252},
     year = {1974},
     volume = {9},
     zbl = {0292.20057},
     url = {http://geodesic.mathdoc.fr/item/SF_1974__9_134080/}
}