@article{JIS_2005__8_1_a3,
     author = {Stay,  Michael},
     title = {Generalized number derivatives},
     journal = {Journal of integer sequences},
     year = {2005},
     volume = {8},
     number = {1},
     zbl = {1065.05019},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JIS_2005__8_1_a3/}
}