Subba Rao, M. V. “On the Existence of a Norm Weaker Than a Given Family of Norms on a Vector Space”. The Journal of the Indian Mathematical Society 22, no. 2 (June 1, 1958): 53–58. Accessed April 28, 2024. https://www.informaticsjournals.com/index.php/jims/article/view/16975.