@article{10_4064_ap_27_1_21_28,
     author = {Jan Bochenek},
     title = {Oscillation theorems and nodes of eigenfunctions of certain differential equations of the fourth order},
     journal = {Annales Polonici Mathematici},
     pages = {21--28},
     publisher = {mathdoc},
     volume = {27},
     number = {1},
     year = {1972},
     doi = {10.4064/ap-27-1-21-28},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ap-27-1-21-28/}
}