Caponetti, D., Trombetta, A., & Trombetta, G. (2019). Optimal retraction problem for proper $k$-ball-contractive mappings in $C^m [0,1]$. Topological Methods in Nonlinear Analysis, 53(1), 111–125. Retrieved from https://apcz.umk.pl/TMNA/article/view/TMNA.2018.041