@article{IM2_1990_35_3_a3,
     author = {G. M. Gubreev},
     title = {Spectral analysis of biorthogonal expansions of functions, and exponential series},
     journal = {Izvestiya. Mathematics },
     pages = {573--605},
     publisher = {mathdoc},
     volume = {35},
     number = {3},
     year = {1990},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1990_35_3_a3/}
}