Meenakshi, Ar., and D. Krishnaswamy. “Principal Pivot Transforms of Range Symmetric Matrices in Minkowski Space”. Tamkang Journal of Mathematics 37, no. 3 (September 30, 2006): 211-219. Accessed October 18, 2021. https://journals.math.tku.edu.tw/index.php/TKJM/article/view/166.