Caponetti D, Trombetta A, Trombetta G. Optimal retraction problem for proper $k$-ball-contractive mappings in $C^m [0,1]$. TMNA [Internet]. 2019 Feb. 17 [cited 2024 Jul. 22];53(1):111-25. Available from: https://apcz.umk.pl/TMNA/article/view/TMNA.2018.041