@article{MS2_1957__5_165645,
     author = {JAAK PEETRE},
     title = {A generalization of {Courant's} nodal domain theorem..},
     journal = {Mathematica Scandinavica},
     pages = {15--20},
     publisher = {mathdoc},
     volume = {5},
     year = {1957},
     zbl = {0077.30101},
     url = {http://geodesic.mathdoc.fr/item/MS2_1957__5_165645/}
}