Strouboulis, T., Copps, K., & Babuska, I.
(2001).The generalized finite element method. Computer Methods in Applied Mechanics and Engineering.
190(32-33), 4081-4193.
Babuska, I., Strouboulis, T., Gangaraj, S. K., Copps, K., & Datta, D. K.
(1998).A-posteriori estimation of the error in the error estimate. Studies in Applied Mechanics.
Advances in Adaptive Computational Methods in Mechanics.
(pp. 155-197).
Elsevier.