@book{MSM_1938__90__1_0,
     author = {Trjitzinsky, W. J.},
     title = {Analytic theory of non-linear singular differential equations},
     series = {M\'emorial des sciences math\'ematiques},
     publisher = {Gauthier-Villars},
     number = {90},
     year = {1938},
     zbl = {0020.12304},
     language = {en},
     url = {http://www.numdam.org/item/MSM_1938__90__1_0/}
}