@inproceedings{james1964the, title={The functional equation$f$^{$n$}($x$)=$g$($x$)}, author={James C. Lillo}, url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203432241956026}, booktitle={Arkiv for Matematik}, volume={5}, number={3}, pages={357-361}, year={1964}, }