@article{NUMA_1972__19_132133,
     author = {G. Strang},
     title = {Approximation in the {Finite} {Element} {Method.}},
     journal = {Numerische Mathematik},
     pages = {81--98},
     publisher = {mathdoc},
     volume = {19},
     year = {1972},
     zbl = {0221.65174},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1972__19_132133/}
}