@article{NUMA_1981__37_132734,
     author = {P. Neittaanm\"aki and J. Saranen},
     title = {On {Finite} {Element} {Approximation} of the {Gradient} for {Solution} of {Poisson} {Equation.}},
     journal = {Numerische Mathematik},
     pages = {333--338},
     publisher = {mathdoc},
     volume = {37},
     year = {1981},
     zbl = {0463.65073},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1981__37_132734/}
}