@article{AM2_1987__33_137216,
     author = {C. Praagman},
     title = {Roots, iterations and logarithms of formal automorphisms.},
     journal = {Aequationes mathematicae},
     pages = {251--259},
     year = {1987},
     volume = {33},
     zbl = {0646.39006},
     url = {http://geodesic.mathdoc.fr/item/AM2_1987__33_137216/}
}