1. Good approximation and characterization of subgroups of R/Z;Biró;Studia Sci. Math. Hungar.,2001
2. P. Liardet, oral communication.
3. Good approximations and continued fractions;Kraaikamp;Proc. Amer. Math. Soc.,1991
4. On a series of cosecants related to a problem in ergodic theory;Petersen;Compositio Math.,1973
5. Generalized arithmetical progressions and sumsets;Ruzsa;Acta Math. Hungar.,1994