Pandey, P. N., and Manish Kumar Gupta. “On a Four-Dimensional Berwald Space With Vanishing H-Connection Vector $ k_i$”. Tamkang Journal of Mathematics 39, no. 2 (June 30, 2008): 121–130. Accessed November 21, 2024. https://journals.math.tku.edu.tw/index.php/TKJM/article/view/22.