@article{GDZPPN001173340,
title = {Pointwise Lower and Upper Bounds for Eigenfunctions of Ordinary Differential Operators.},
journal = {Numerische Mathematik},
volume = {26},
year = {1976},
pages = {111-120},
zbl = {0324.65040},
url = {http://dml.mathdoc.fr/item/GDZPPN001173340}
}
Küpper, T. Pointwise Lower and Upper Bounds for Eigenfunctions of Ordinary Differential Operators.. Numerische Mathematik, Tome 26 (1976) pp. 111-120. http://gdmltest.u-ga.fr/item/GDZPPN001173340/