Ira M. Gessel. A q-analog of the exponential formula. Discrete Mathematics, 40(1):69-80, 1982. [doi]
@article{Gessel82,
title = {A q-analog of the exponential formula},
author = {Ira M. Gessel},
year = {1982},
doi = {10.1016/0012-365X(82)90189-3},
url = {http://dx.doi.org/10.1016/0012-365X(82)90189-3},
researchr = {https://researchr.org/publication/Gessel82},
cites = {0},
citedby = {0},
journal = {Discrete Mathematics},
volume = {40},
number = {1},
pages = {69-80},
}