@article{10_14708_ma_v11i22_1591,
     author = {Maciej Szymkat},
     title = {The form of the n-th iteration of the operator q=fd/dx},
     journal = {Mathematica Applicanda},
     pages = { 227--249},
     publisher = {mathdoc},
     volume = {11},
     number = {22},
     year = {1983},
     doi = {10.14708/ma.v11i22.1591},
     language = {pl},
     url = {http://geodesic.mathdoc.fr/articles/10.14708/ma.v11i22.1591/}
}