@article{ASNSP_1987_4_14_1_1_0,
     author = {Egnell, Henrik},
     title = {Extremal properties of the first eigenvalue of a class of elliptic eigenvalue problems},
     journal = {Annali della Scuola Normale Superiore di Pisa - Classe di Scienze},
     pages = {1--48},
     publisher = {Scuola normale superiore},
     volume = {Ser. 4, 14},
     number = {1},
     year = {1987},
     mrnumber = {937535},
     zbl = {0649.35072},
     language = {en},
     url = {http://www.numdam.org/item/ASNSP_1987_4_14_1_1_0/}
}