@article{AFM_1999_24_2_a5,
     author = {G. Frank and J.K. Langley},
     title = {On the zeros of pairs of linear differential polynomials},
     journal = {Annales Fennici Mathematici},
     pages = {409--436},
     publisher = {mathdoc},
     volume = {24},
     number = {2},
     year = {1999},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/AFM_1999_24_2_a5/}
}