Lupşa, Liana. “I-Points With Respect to a Given Set”. Anal. Numér. Théor. Approx. 15, no. 2 (August 1, 1986): 145–147. Accessed April 14, 2025. https://ictp.acad.ro/jnaat/journal/article/view/1986-vol15-no2-art8.