@article{ADM_2006_4_a8,
     author = {A. Stronska},
     title = {Nilpotent subsemigroups of a~semigroup of order-decreasing transformations of a~rooted tree},
     journal = {Algebra and discrete mathematics},
     pages = {126--140},
     publisher = {mathdoc},
     number = {4},
     year = {2006},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ADM_2006_4_a8/}
}