1. Berkes, I.: Almost sure invariance principles for mixing processes. [To appear in Ann. Probability]
2. Gapo?kin, V.F.: Lacunary series and independent functions (In Russian). Uspehi Mat. Nauk 21, 3?82 (1966). English translation: Russian Math. Surveys 21, 3?82 (1966)
3. Gapo?kin, V.F.: On some sequences of almost independent functions (In Russian). Sibirsk Mat. ?. 9, 264?279 (1968)
4. Gapo?kin, V.F.: On the central limit theorem for some weakly dependent sequences (In Russian). Teor. Verojatnost. i. Primenen. 15, 666?684 (1970). English translation: Theor. Probability Appl. 15, 649?666 (1970)
5. Hartman, P.: The divergence of non-harmonic gap series. Duke Math. J. 9, 404?405 (1942)