@article{1102635617, author = {Engman, Martin}, title = {New spectral characterization theorems for $S^2$.}, journal = {Pacific J. Math.}, volume = {156}, number = {2}, year = {1992}, pages = { 215-229}, language = {en}, url = {http://dml.mathdoc.fr/item/1102635617} }
Engman, Martin. New spectral characterization theorems for $S^2$.. Pacific J. Math., Tome 156 (1992) no. 2, pp. 215-229. http://gdmltest.u-ga.fr/item/1102635617/