@article{NUMA_1961__3_131470,
     author = {N.J. LEHMANN},
     title = {Das inhomogene nat\"urliche {Randwertproblem} und {Fehlerabsch\"atzungen} f\"ur {N\"aherungsl\"osungen.}},
     journal = {Numerische Mathematik},
     pages = {1--29},
     publisher = {mathdoc},
     volume = {3},
     year = {1961},
     zbl = {0097.07102},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1961__3_131470/}
}