Godini, G. “A Generalization of Set-Valued Metric Projections”. Anal. Numér. Théor. Approx. 12, no. 1 (February 1, 1983): 25–44. Accessed November 23, 2024. https://ictp.acad.ro/jnaat/journal/article/view/1983-vol12-no1-art4.