LAZAROV, Raytcho, REPIN, Sergey and TOMAR, Satyendra, 2008, Functional a posteriori error estimates for discontinuous Galerkin approximations of elliptic problems. Numerical methods for partial differential equations [online]. 2008. Vol. 25, no. 4, p. 952–971. [Accessed 6 January 2025]. DOI 10.1002/num.20386. Retrieved from: https://doi.org/10.1002/num.20386