Cobzaş, Ştefan, and C. Mustăţa. “Selections Associated to the Metric Projection”. Rev. Anal. Numér. Théor. Approx. 24, no. 1 (August 1, 1995): 45–52. Accessed August 10, 2022. https://ictp.acad.ro/jnaat/journal/article/view/1995-vol24-nos1-2-art5.