@article{ADM_2010_9_2_a8,
     author = {A. Umar},
     title = {Some combinatorial problems in the theory of symmetric inverse semigroups},
     journal = {Algebra and discrete mathematics},
     pages = {115--126},
     publisher = {mathdoc},
     volume = {9},
     number = {2},
     year = {2010},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ADM_2010_9_2_a8/}
}