Chivu Cojocaru, Mariana, and Andaluzia Matei. “Weak Solutions via Two-Field Lagrange Multipliers for Boundary Value Problems in Mathematical Physics”. Mathematical Modelling and Analysis 27, no. 4 (November 10, 2022): 561–572. Accessed April 11, 2025. https://jest.vgtu.lt/index.php/MMA/article/view/15827.