See:
- CIMRM Supplement - Mithraeum. Riegel, nr. Frieburg in Brisgau, Germany.-http://www.tertullian.org/rpearse/mithras/display.php?page=supp_Germany_Riegel_Mithraeum
- B. Cammerer, "Riegel Mithraeum", in: Filtzinger, Ph., D. Planck & B. Cammerer. Roemer in Baden-Wuettemberg, 3. Auflage. Stuttgart, pp. 506-508.
- https://www.lieux-insolites.fr/allemagne/riegel/riegel.htm