@article{IM2_1987_28_3_a1,
     author = {P. G. Grinevich},
     title = {Vector rank of commuting matrix differential operators. {Proof} of {S.} {P.~Novikov's} criterion},
     journal = {Izvestiya. Mathematics},
     pages = {445--465},
     year = {1987},
     volume = {28},
     number = {3},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1987_28_3_a1/}
}