@article{GDZPPN001170287, title = {Approximation in the Finite Element Method.}, journal = {Numerische Mathematik}, volume = {19}, year = {1972}, pages = {81-98}, zbl = {0221.65174}, url = {http://dml.mathdoc.fr/item/GDZPPN001170287} }
Strang, G. Approximation in the Finite Element Method.. Numerische Mathematik, Tome 19 (1972) pp. 81-98. http://gdmltest.u-ga.fr/item/GDZPPN001170287/