@article{EJDE_2003__2003__a116,
     author = {Sokolov,  Maksim S.},
     title = {An abstract approach to some spectral problems of direct sum differential operators},
     journal = {Electronic journal of differential equations},
     year = {2003},
     volume = {2003},
     zbl = {1045.47016},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EJDE_2003__2003__a116/}
}