Geodesic
Finite groups of outer automorphisms of free groups
Glasgow mathematical journal, Tome 38 (1996) no. 3, pp. 275-282

Voir la notice de l'article provenant de la source Cambridge University Press

Let Fr denote the free group of rank r and Out Fr: = AutFr/Inn Fr the outer automorphism group of Fr (automorphisms modulo inner automorphisms). In [10] we determined the maximal order 2rr! (for r > 2) for finite subgroups of Out Fr as well as the finite subgroup of that order which, for r > 3, is unique up to conjugation. In the present paper we determine all maximal finite subgroups (that is not contained in a larger finite subgroup) of Out F3, up to conjugation (Theorem 2 in Section 3). Here the considered case r = 3 serves as a model case: our method can be applied for other small values of r (in principle for any value of r) but the computations become considerably longer and are more apt for a computer then; the method can also be applied to determine the maximal finite subgroups of the automorphism group Aut Fr of Fr. Note that the canonical projection Aut Fr ⃗ Out Fr is injective on finite subgroups of Aut Fr; however, not all finite subgroups of Out Fr lift to finite subgroups of Aut Fr. 
Zimmermann, Bruno. Finite groups of outer automorphisms of free groups. Glasgow mathematical journal, Tome 38 (1996) no. 3, pp. 275-282. doi: 10.1017/S0017089500031700
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