1. Baragar, A.: Asymptotic Growth of Markoff-Hurwitz Numbers. Compositio Math.94, 1?18 (1994).
2. Baragar, A.: Products of Consecutive Integers and the Markoff Equation. Aequationes Math. (to appear)
3. Batyrev, V. V., Manin, Yu. I.: Sur le nombre des points rationnels de hauteur born� des vari�t�s alg�briques. Math. Ann.286, 27?43 (1990).
4. Cassels J. W. S.: An Introduction to Diophantine Approximation. Cambridge: Cambridge University Press 1957.
5. Cusick, T. W.: On Perrine's Generalized Markoff Equations. Aequationes Math.46, 203?211 (1993).