@article{SF_1992__45_3_135170,
     author = {B. Billhardt},
     title = {On a wreath product embedding  and idempotent   pure congruences on inverse semigroups.},
     journal = {Semigroup forum},
     pages = {45--54},
     publisher = {mathdoc},
     volume = {45},
     number = {3},
     year = {1992},
     zbl = {0769.20027},
     url = {http://geodesic.mathdoc.fr/item/SF_1992__45_3_135170/}
}