We give a set of sufficient conditions for the existence of differentiable solutions for a functional equation involving a series of iterates, using a method different from that of Baker and Zhang [Ann. Polon. Math. 73 (2000)].
@article{bwmeta1.element.bwnjournal-article-doi-10_4064-ap92-3-3, author = {V. Murugan and P. V. Subrahmanyam}, title = {Differentiable solutions for a class of functional equations}, journal = {Annales Polonici Mathematici}, volume = {92}, year = {2007}, pages = {225-241}, zbl = {1156.39012}, language = {en}, url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-ap92-3-3} }
V. Murugan; P. V. Subrahmanyam. Differentiable solutions for a class of functional equations. Annales Polonici Mathematici, Tome 92 (2007) pp. 225-241. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-ap92-3-3/