@article{10_4153_CJM_1987_040_8,
     author = {Brownawell, W. Dale},
     title = {On {The} {Factorization} of {Partial} {Differential} {Equations}},
     journal = {Canadian journal of mathematics},
     pages = {825--834},
     year = {1987},
     volume = {39},
     number = {4},
     doi = {10.4153/CJM-1987-040-8},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1987-040-8/}
}