CRISTEA, Valentin Gabriel. A direct approach for proving Wallis ratio estimates and an improvement of Zhang-Xu-Situ inequality. Studia Universitatis Babeș-Bolyai Mathematica, [S. l.], v. 60, n. 2, p. 201–209, 2015. Disponível em: https://studia.reviste.ubbcluj.ro/index.php/subbmathematica/article/view/5718. Acesso em: 5 feb. 2025.