Mapping tori of free group automorphisms are coherent. Feighn, Mark, Handel, Michael (1999) Annals of Mathematics. Second Series
Maximal index automorphisms of free groups with no attracting fixed points on the boundary are Dehn twists. Martino, Armando (2002) Algebraic & Geometric Topology
Monomorphisms of finitely generated free groups have finitely generated equalizers. R.Z. Goldstein, E.G. Turner (1985) Inventiones mathematicae
Most automorphisms of a hyperbolic group have very simple dynamics Gilbert Levitt, Martin Lustig (2000) Annales scientifiques de l'École Normale Supérieure