A Conceptual Framework of Convex and Concave Sets under Refined Intuitionistic Fuzzy Set Environment. Journal of Prime Research in Mathematics, [S. l.], v. 17, n. 2, p. 122 – 137, 2021. Disponível em: https://jprm.sms.edu.pk/index.php/jprm/article/view/178. Acesso em: 7 dec. 2025.