@article{IM2_1968_2_4_a1,
     author = {V. I. Plotnikov},
     title = {An energy inequality and the overdeterminacy property of a system of eigenfunctions},
     journal = {Izvestiya. Mathematics},
     pages = {695--707},
     year = {1968},
     volume = {2},
     number = {4},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1968_2_4_a1/}
}