@article{JMAG_2014_10_1_a1,
     author = {A. M. Kholkin and F. S. Rofe-Beketov},
     title = {On {Spectrum} of {Differential} {Operator} with {Block-Triangular} {Matrix} {Coefficients}},
     journal = {\v{Z}urnal matemati\v{c}eskoj fiziki, analiza, geometrii},
     pages = {44--63},
     year = {2014},
     volume = {10},
     number = {1},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JMAG_2014_10_1_a1/}
}