Braga, F., G. Rega, and F. Vestroni. “Numerical Analysis of Compatible Finite Elements of Different Order in Two-Dimensional Problems of Elasticity”. Engineering Transactions 26, no. 4 (December 30, 1978): 619–643. Accessed June 9, 2025. https://et3.ippt.pan.pl/index.php/et/article/view/2147.