@article{GDZPPN00206197X,
title = {Eigenfunctions and Nodal Sets},
journal = {Commentarii mathematici Helvetici},
volume = {51},
year = {1976},
pages = {43-56},
zbl = {0334.35022},
url = {http://dml.mathdoc.fr/item/GDZPPN00206197X}
}
Cheng, Shiu-Yuen. Eigenfunctions and Nodal Sets. Commentarii mathematici Helvetici, Tome 51 (1976) pp. 43-56. http://gdmltest.u-ga.fr/item/GDZPPN00206197X/