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2. Bestvina, M.: A Bers-like proof of the existence of train tracks for free group automorphisms. Fund. Math. 214(1), 1–12 (2011)
3. Bestvina, M., Handel, M.: Train tracks and automorphisms of free groups. Ann. Math. 135(1), 1–51 (1992)
4. Bestvina, M., Feighn, M., Handel, M.: Laminations, trees, and irreducible automorphisms of free groups. Geom. Funct. Anal. 7(2), 215–244 (1997)
5. Bestvina, M., Guirardel, V., Horbez, C.: Boundary amenability of $$Out(F_N)$$. arXiv:1705.07017 (2017)