Gregorii I papae Registrvm epistolarvm.
APA Citation
Catholic Church. Pope (590-604 : Gregory I)., Pelagius II, P., Hartmann, L. Moritz., Ewald, P. (189199). Gregorii I papae Registrvm epistolarvm. Berolini: apvd Weidmannos.
MLA Citation
Catholic Church. Pope (590-604 : Gregory I), Pope Pelagius II, Ludo Moritz Hartmann, and Paul Ewald. Gregorii I Papae Registrvm Epistolarvm. Berolini: apvd Weidmannos, 189199.
Warning: These citations may not always be complete (especially for serials).