@article{Chaoha_Goebel_Termwuttipong_2012, title={Around Ulam’s question on retractions}, volume={40}, url={https://apcz.umk.pl/TMNA/article/view/TMNA.2012.029}, abstractNote={It is known that the unit ball in infinitely dimensional Hilbert space can be retracted onto its boundary via a lipschitzian mapping. The magnitude of Lipschitz constant is only roughly estimated. The note contains a number of observations connected to this result and opens some new problems.}, number={1}, journal={Topological Methods in Nonlinear Analysis}, author={Chaoha, Phichet and Goebel, Kazimierz and Termwuttipong, Imchit}, year={2012}, month={Apr.}, pages={215–224} }