Berg, I. D. On functions with almost periodic or almost automorphic first differences. (English) Zbl 0186.14201 J. Math. Mech. 19, 239-245 (1969). PDFBibTeX XMLCite \textit{I. D. Berg}, J. Math. Mech. 19, 239--245 (1969; Zbl 0186.14201)
Lowenthal, F. Transitive subsemigroups of the Moebius group. (English) Zbl 0162.10601 J. Math. Mech. 18, 173-189 (1968). PDFBibTeX XMLCite \textit{F. Lowenthal}, J. Math. Mech. 18, 173--189 (1968; Zbl 0162.10601)