@article{JIS_2007__10_8_a1,
     author = {Male\v{s}evi\'c,  Branko J. and Jovovi\'c,  Ivana V.},
     title = {The compositions of differential operations and the {G\^ateaux} directional derivative},
     journal = {Journal of integer sequences},
     year = {2007},
     volume = {10},
     number = {8},
     zbl = {1149.05313},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JIS_2007__10_8_a1/}
}