@article{RCP25_1972__14__A4_0,
     author = {G\'erard, R. and Levelt, A. H. M.},
     title = {Invariants mesurant l'irr\'egularit\'e en un point singulier des syst\`emes d'\'equations diff\'erentielles lin\'eaires},
     journal = {Les rencontres physiciens-math\'ematiciens de Strasbourg -RCP25},
     note = {talk:4},
     pages = {1--35},
     publisher = {Institut de Recherche Math\'ematique Avanc\'ee - Universit\'e Louis Pasteur},
     volume = {14},
     year = {1972},
     language = {fr},
     url = {http://archive.numdam.org/item/RCP25_1972__14__A4_0/}
}