@article{10_4064_ap_16_2_153_167,
     author = {Jan Bochenek},
     title = {On some problems in the theory of eigenvalues and eigenfunctions associated with linear elliptic partial differential equations of the second order},
     journal = {Annales Polonici Mathematici},
     pages = {153--167},
     publisher = {mathdoc},
     volume = {16},
     number = {2},
     year = {1964},
     doi = {10.4064/ap-16-2-153-167},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ap-16-2-153-167/}
}