Mustăţa, Costică. “A Characterisation of Chebyshevian Subspace of \(y^{\perp}\)-Type”. Anal. Numér. Théor. Approx. 6, no. 1 (February 1, 1977): 51–56. Accessed September 4, 2025. https://www.ictp.acad.ro/jnaat/journal/article/view/1977-vol6-no1-art8.