Cimoca, G. “On a Problem of Simultaneous Best Approximation”. Rev. Anal. Numér. Théorie Approximation 3, no. 1 (February 1, 1974): 23–26. Accessed September 4, 2025. https://www.ictp.acad.ro/jnaat/journal/article/view/1974-vol3-no1-art3.