@article{IM_1987__87_143412,
     author = {N.M. Katz},
     title = {On the calculation of some differential galois groups.},
     journal = {Inventiones mathematicae},
     pages = {13--62},
     publisher = {mathdoc},
     volume = {87},
     year = {1987},
     zbl = {0609.12025},
     url = {http://geodesic.mathdoc.fr/item/IM_1987__87_143412/}
}