@article{CMH_1976__51_139642,
     author = {Shiu-Yuen Cheng},
     title = {Eigenfunctions and {Nodal} {Sets}},
     journal = {Commentarii mathematici Helvetici},
     pages = {43--56},
     publisher = {mathdoc},
     volume = {51},
     year = {1976},
     zbl = {0334.35022},
     url = {http://geodesic.mathdoc.fr/item/CMH_1976__51_139642/}
}