1. [A]A. Avez, Variétés riemanniennes sans points focaux. C.R.A.S. A-B 270 (1970), A 188–191.
2. [B]I. Babenko, Asymptotic volume of tori and geometry of convex bodies, Mat. Zametki 44:2 (1988), 177–188.
3. [Ba1]V. Bangert, Minimal geodesics, Erg. Theory and Dyn. Syst. 10 (1990), 263–286.
4. [Ba2]V. Bangert, Geodesic rays, Busemann functions and monotone twist maps. Calc. Var. 2 (1994), 49–63.
5. [Bu1]D. Burago, Periodic metrics, Advances in Soviet Math. 9, New York (1992), 205–210.