Mustăţa, Costică. “On the Metric Projection and the Quotient Mapping”. Rev. Anal. Numér. Théor. Approx. 24, no. 1 (August 1, 1995): 191–199. Accessed November 8, 2024. https://ictp.acad.ro/jnaat/journal/article/view/1995-vol24-nos1-2-art21.