@article{03977778, title = {Perturbations of normally solvable nonlinear operators. I.}, journal = {International Journal of Mathematics and Mathematical Sciences}, volume = {8}, year = {1985}, pages = {241-246}, doi = {10.1155/S0161171285000266}, zbl = {0605.47056}, language = {en}, url = {http://dml.mathdoc.fr/item/03977778} }
Ray, William O.; Walker, Anita M. Perturbations of normally solvable nonlinear operators. I.. International Journal of Mathematics and Mathematical Sciences, Tome 8 (1985) pp. 241-246. doi : 10.1155/S0161171285000266. http://gdmltest.u-ga.fr/item/03977778/