@article{JSFU_2016_9_1_a4,
     author = {Vasily Yu. Goncharov},
     title = {Existence criteria in some extremum problems involving eigenvalues of elliptic operators},
     journal = {\v{Z}urnal Sibirskogo federalʹnogo universiteta. Matematika i fizika},
     pages = {37--47},
     year = {2016},
     volume = {9},
     number = {1},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JSFU_2016_9_1_a4/}
}