Chang, Kung Ching, and Jiaquan Liu. “A Cohomology Complex for Manifolds With Boundary”. Topological Methods in Nonlinear Analysis 5, no. 2 (June 1, 1995): 325–340. Accessed July 22, 2024. https://apcz.umk.pl/TMNA/article/view/TMNA.1995.022.