Cobzaş, Ş. “On a Theorem of V.N. Nikolski on Characterization of Best Approximation for Convex Sets”. Anal. Numér. Théor. Approx. 19, no. 1 (February 1, 1990): 7–13. Accessed November 21, 2024. https://ictp.acad.ro/jnaat/journal/article/view/1990-vol19-no1-art2.