Nguyen, D. T., and D. Q. Si. “On the Relation Between Curvature, Diameter, and Volume of a Complete Riemannian Manifold”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 56, no. 11, Nov. 2004, pp. 1576–1583, https://umj.imath.kiev.ua/index.php/umj/article/view/3867.