He devoted himself especially to the study of Roman religion, to which he contributed a volume in Iwan Müller’s Handbuch: *Religion und Kultus der Römer* (Munich 1902 and later ed. 1912), still unsurpassed. He edited the new edition of the third part of *Röm. Staatsverwaltung*, dealing with Roman sacred antiquities by J. Marquardt. He began the completely revised and expanded new edition of the *Realencyclopädie* of Pauly, still in progress and enriched with supplements. He also edited the 9th and 10th editions of *Sittengeschichte Roms* by Friedländer (4 vols., 1919–23). His *Gesammelte Abhandlungen zur röm. Religions- und Stadtgeschichte* (1904) contains a valuable collection of studies and research on the subject.
BIBL.: O. Kern, *Neologia di G. W.*, in *Jahresbericht über die Fortschritte der klassischen Altertumswissenschaft* (Bursa), vol. 245 (1934), part 4, pp. 120–45.