@article{1183524270, author = {Block, H. D. and Fuchs, W. H. J.}, title = {An enclosure theorem for eigenvalues}, journal = {Bull. Amer. Math. Soc.}, volume = {67}, number = {6}, year = {1961}, pages = { 425-426}, language = {en}, url = {http://dml.mathdoc.fr/item/1183524270} }
Block, H. D.; Fuchs, W. H. J. An enclosure theorem for eigenvalues. Bull. Amer. Math. Soc., Tome 67 (1961) no. 6, pp. 425-426. http://gdmltest.u-ga.fr/item/1183524270/