TY  - JOUR
AU  - Bernard Helffer
AU  - Pierre H. Bérard
TI  - On Courant's Nodal Domain Property for Linear Combinations of Eigenfunctions. I
JO  - Documenta mathematica
PY  - 2018
SP  - 1561
EP  - 1585
VL  - 23
UR  - http://geodesic.mathdoc.fr/articles/10.4171/dm/652/
DO  - 10.4171/dm/652
ID  - 10_4171_dm_652
ER  -