@incollection{MEM_2012_41_1_a13,
     author = {Dimitrova, Ilinka and Mladenova, Tsvetelina},
     title = {Classification of the {Maximal} {Subsemigroups} of the {Semigroup} of all {Partial} {Order-Preserving} {Transformations}},
     booktitle = {},
     series = {Mathematics and Education in Mathematics},
     pages = {158--162},
     year = {2012},
     volume = {41},
     number = {1},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/MEM_2012_41_1_a13/}
}