Cobzaş, Ştefan, and Ioan Muntean. “Duality Relations and Characterizations of Best Approximation for P-Convex Sets”. Anal. Numér. Théor. Approx. 16, no. 2 (August 1, 1987): 95–108. Accessed August 12, 2022. https://ictp.acad.ro/jnaat/journal/article/view/1987-vol16-no2-art2.