@article{ADM_2007_4_a6,
     author = {Omelyan Gorbachuk and Mykola Komarnytskyi and Yuri Maturin},
     title = {On differential preradicals},
     journal = {Algebra and discrete mathematics},
     pages = {73--83},
     publisher = {mathdoc},
     number = {4},
     year = {2007},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ADM_2007_4_a6/}
}