@article{JMAG_2009_5_2_a1,
     author = {V. M. Bruk},
     title = {On linear relations generated by nonnegative operator function and degenerate elliptic differential-operator expression},
     journal = {\v{Z}urnal matemati\v{c}eskoj fiziki, analiza, geometrii},
     pages = {123--144},
     year = {2009},
     volume = {5},
     number = {2},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JMAG_2009_5_2_a1/}
}