BondarenkoV. V., BondarenkoV. M., and PeregudaYu. N. “Local Deformations of Positive-Definite Quadratic Forms”. Ukrains’kyi Matematychnyi Zhurnal 64, no. 7 (July 25, 2012): 892-907. Accessed July 27, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/2626.