@article{NUMA_1991__59_8_133553,
     author = {E.F. D'Azevedo and R.B. Simpson},
     title = {On optimal triangular meshes for minimizing the gradient error.},
     journal = {Numerische Mathematik},
     pages = {321--348},
     publisher = {mathdoc},
     volume = {59},
     number = {8},
     year = {1991},
     zbl = {0724.65006},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1991__59_8_133553/}
}