@article{ADM_2016_22_2_a10,
     author = {Anatolii V. Zhuchok and Milan Demko},
     title = {Free $n$-dinilpotent doppelsemigroups},
     journal = {Algebra and discrete mathematics},
     pages = {304--316},
     publisher = {mathdoc},
     volume = {22},
     number = {2},
     year = {2016},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ADM_2016_22_2_a10/}
}