CRISTEA, Valentin Gabriel. “A Direct Approach for Proving Wallis Ratio Estimates and an Improvement of Zhang-Xu-Situ Inequality”. Studia Universitatis Babeș-Bolyai Mathematica 60, no. 2 (June 30, 2015): 201–209. Accessed February 5, 2025. https://studia.reviste.ubbcluj.ro/index.php/subbmathematica/article/view/5718.