NesterenkoA. N., and PetrovaT. O. “On One Problem for Comonotone Approximation”. Ukrains’kyi Matematychnyi Zhurnal 57, no. 10 (October 25, 2005): 1424–1429. Accessed November 22, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3697.