@article{GDZPPN002040158,
title = {On the stabiltiy of a system of functional equations characterizing generalize hyperbolic and trigonometric functions.},
journal = {Aequationes mathematicae},
volume = {45},
year = {1993},
pages = {285-296},
zbl = {0774.39007},
url = {http://dml.mathdoc.fr/item/GDZPPN002040158}
}
Schwaiger, Jens; Förg-Rob, Wolfgang. On the stabiltiy of a system of functional equations characterizing generalize hyperbolic and trigonometric functions.. Aequationes mathematicae, Tome 45 (1993) pp. 285-296. http://gdmltest.u-ga.fr/item/GDZPPN002040158/