@article{ISU_2009_9_1_a4,
     author = {V. S. Rykhlov},
     title = {On properties of the eigenfunctions of a~quadratic pencil of the second order differential operators},
     journal = {Izvestiya of Saratov University. Mathematics. Mechanics. Informatics},
     pages = {31--44},
     publisher = {mathdoc},
     volume = {9},
     number = {1},
     year = {2009},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ISU_2009_9_1_a4/}
}