Blum Julius R.: Ergodic sequences of integers. In: Acta scientiarum mathematicarum, (46). pp. 243-247. (1983)
Blum Julius R.; Eisenberg Bennett; Hahn Liang Shin: Ergodic theory and the measure of sets in the Bohr group. In: Acta scientiarum mathematicarum, (34). pp. 17-24. (1973)