Hijmans 2024, pp. 1019–1020: "Support for the 25th of December as date of the Solar Games is sought in the enigmatic entry for that day in the Chronography of 354 ("N. Invicti c. m. XXX") and from the emperor Julian, who wrote early in 363 that he had celebrated a 'most magnificent agon' for Sol at the end of December right after the Saturnalia of the preceding year. ... But a closer look at Julian's hymn (Or. 4) shows that this is not the case ... Julian is clearly talking about two different celebrations of Sol. The first is an annual feast ... The second are the quadrennial games, which Julian qualifies as 'newish' ... Julian makes it quite clear that it was the 'old' festival of Sol, which he ascribes to Numa, that he had celebrated immediately after the end of the Saturnalia to coincide with the winter solstice." Hijmans, S. E. (2024). Sol: Image and Meaning of the Sun in Roman Art and Religion. Brill. ISBN978-90-04-52158-2.
Hijmans 2009, Chapter 1 (a reworking of Hijmans (1996)); Matern 2002; Wallraff 2001; and Berrens 2004 all follow Hijmans. Hijmans, Steven Ernst (2009). Sol: The Sun in the Art and Religions of Rome (Thesis). Groningen: University of Groningen. hdl:11370/af334f2a-d157-4793-95c6-80d2f6323668. ISBN978-90-367-3931-3. Retrieved 2025-02-26. Matern, Petra (2002). Helios und Sol: Kulte und Ikonographie des griechischen und römischen Sonnengottes [Helios and Sol: Cults and Iconography of the Greek and Roman Sun God] (in German). Ege Yayınları. ISBN978-975-8070-53-4. OCLC53857589. Wallraff, Martin (2001). Christus versus Sol. Sonnenverehrung und Christentum in der Spätantike [Christ versus Sol. Sun Worship and Christianity in Late Antiquity]. Münster: Aschendorff. ISBN3-402-08115-6. Berrens, Stephan (2004). Sonnenkult und Kaisertum von den Severern bis zu Constantin I. (193–337 n. Chr.) [Sun worship and empire from the Severans to Constantine I (193-337 AD)]. Historia-Einzelschriften (in German). Vol. 185. Stuttgart: Franz Steiner Verlag. ISBN978-3-515-08575-5. OCLC57010712.
Hijmans 2009, p. 570: "To explain the presence of Sol in a Christian mausoleum, scholars suggested that in this case he was not Sol, but Christ depicted in the guise of Sol as the New Light and the Sun of Justice. In the words of Lawrence: 'This is the Sun God, Sol Invictus, but also Christ the light of the world' ... Sol in mausoleum M has become the image of choice to illustrate the gradual ascendency of Christianity in the third century AD and in particular of its appropriation of Roman imagery for Christian purposes. ... While Perler, Wallraff, and others differ on details of the meaning of this Sol-Christ, all agree on the basic Christian interpretation and the identity of Sol as Christ". Hijmans, Steven Ernst (2009). Sol: The Sun in the Art and Religions of Rome (Thesis). Groningen: University of Groningen. hdl:11370/af334f2a-d157-4793-95c6-80d2f6323668. ISBN978-90-367-3931-3. Retrieved 2025-02-26.
Matern 2002. Matern, Petra (2002). Helios und Sol: Kulte und Ikonographie des griechischen und römischen Sonnengottes [Helios and Sol: Cults and Iconography of the Greek and Roman Sun God] (in German). Ege Yayınları. ISBN978-975-8070-53-4. OCLC53857589.
Berrens 2004. Berrens, Stephan (2004). Sonnenkult und Kaisertum von den Severern bis zu Constantin I. (193–337 n. Chr.) [Sun worship and empire from the Severans to Constantine I (193-337 AD)]. Historia-Einzelschriften (in German). Vol. 185. Stuttgart: Franz Steiner Verlag. ISBN978-3-515-08575-5. OCLC57010712.
Hijmans 2009, Chapter 1 (a reworking of Hijmans (1996)); Matern 2002; Wallraff 2001; and Berrens 2004 all follow Hijmans. Hijmans, Steven Ernst (2009). Sol: The Sun in the Art and Religions of Rome (Thesis). Groningen: University of Groningen. hdl:11370/af334f2a-d157-4793-95c6-80d2f6323668. ISBN978-90-367-3931-3. Retrieved 2025-02-26. Matern, Petra (2002). Helios und Sol: Kulte und Ikonographie des griechischen und römischen Sonnengottes [Helios and Sol: Cults and Iconography of the Greek and Roman Sun God] (in German). Ege Yayınları. ISBN978-975-8070-53-4. OCLC53857589. Wallraff, Martin (2001). Christus versus Sol. Sonnenverehrung und Christentum in der Spätantike [Christ versus Sol. Sun Worship and Christianity in Late Antiquity]. Münster: Aschendorff. ISBN3-402-08115-6. Berrens, Stephan (2004). Sonnenkult und Kaisertum von den Severern bis zu Constantin I. (193–337 n. Chr.) [Sun worship and empire from the Severans to Constantine I (193-337 AD)]. Historia-Einzelschriften (in German). Vol. 185. Stuttgart: Franz Steiner Verlag. ISBN978-3-515-08575-5. OCLC57010712.