1. C. Perin and R. Sklinos, “Homogeneity in the free groups,” Duke Math. J., 161, No. 13, 2635-2668 (2012).
2. D. Marker, Model Theory: An Introduction, Grad. Texts Math., 217, Springer, New York (2002).
3. A. Nies, “Aspects of free groups,” J. Alg., 263, No. 1, 119-125 (2003).
4. A. Ould Houcine, “Homogeneity and prime models in torsion-free hyperbolic groups,” Confl. Math., 3, No. 1, 121-155 (2011).
5. W. Hodges, Model Theory, Enc. Math. Appl., 42, Cambridge Univ. Press, Cambridge (1993).