Petrova, Ludmila. “Nonidentical Relations of Skew-Symmetric Forms: Generation of Closed Exterior Forms. Discrete Transitions. Connection Between Field-Theory Equations and Nonidentical Relations”. International Journal of Advanced Mathematical Sciences 4, no. 2 (October 8, 2016): 30–36. Accessed May 4, 2024. https://sciencepubco.com/index.php/IJAMS/article/view/6635.