@article{NUMA_1990__57_6-7_133453,
     author = {John W. Barrett and R.M. Shanahan},
     title = {Total {Flux} {Estimates} for a {Finite} {Element} {Approximation} of the {Dirichlet} {Problem} {Using} the {Boundary} {Penalty} {Method.}},
     journal = {Numerische Mathematik},
     pages = {351--364},
     publisher = {mathdoc},
     volume = {57},
     number = {6-7},
     year = {1990},
     zbl = {0702.65088},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1990__57_6-7_133453/}
}