@article{1102978251,
author = {Headley, V. B.},
title = {A monotonicity principle for eigenvalues.},
journal = {Pacific J. Math.},
volume = {31},
number = {3},
year = {1969},
pages = { 663-668},
language = {en},
url = {http://dml.mathdoc.fr/item/1102978251}
}
Headley, V. B. A monotonicity principle for eigenvalues.. Pacific J. Math., Tome 31 (1969) no. 3, pp. 663-668. http://gdmltest.u-ga.fr/item/1102978251/