@article{ADM_2014_17_1_a7,
     author = {A. Umar},
     title = {Some combinatorial problems in the theory of partial transformation semigroups},
     journal = {Algebra and discrete mathematics},
     pages = {110--134},
     publisher = {mathdoc},
     volume = {17},
     number = {1},
     year = {2014},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ADM_2014_17_1_a7/}
}