@article{JRAM_1976__288_151813,
     author = {U. Kirchgraber},
     title = {Error estimation for perturbed systems.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {202--206},
     publisher = {mathdoc},
     volume = {288},
     year = {1976},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1976__288_151813/}
}