Precup, Radu. “La théorème Des Contractions Dans Des Espaces syntopogènes: The Contraction Theorem in Syntopogenic Spaces”. Anal. Numér. Théor. Approx. 9, no. 1 (February 1, 1980): 113–123. Accessed April 27, 2024. https://ictp.acad.ro/jnaat/journal/article/view/1980-vol9-no1-art15.