@article{ADM_2013_16_1_a12,
     author = {E. D. Schwab},
     title = {Inverse semigroups generated by group congruences. {The} {M\"{o}bius} functions},
     journal = {Algebra and discrete mathematics},
     pages = {116--126},
     publisher = {mathdoc},
     volume = {16},
     number = {1},
     year = {2013},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ADM_2013_16_1_a12/}
}