@article{GDZPPN00231939X, title = {Perturbation of Harmonie Spaces.}, journal = {Mathematische Annalen}, volume = {250}, year = {1980}, pages = {111-122}, zbl = {0421.31009}, url = {http://dml.mathdoc.fr/item/GDZPPN00231939X} }
Hansen, W. Perturbation of Harmonie Spaces.. Mathematische Annalen, Tome 250 (1980) pp. 111-122. http://gdmltest.u-ga.fr/item/GDZPPN00231939X/