@article{JRAM_1987__377_152931,
     author = {Kunrui Yu},
     title = {A generalization of {Mahler's} classification to several variables.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {113--126},
     publisher = {mathdoc},
     volume = {377},
     year = {1987},
     zbl = {0614.10031},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1987__377_152931/}
}