Schaff, Philip. History of the Christian Church (The Complete Eight Volumes in One). Amazon Kindle Edition, 2014.
Volume 2, Ante-Nicene Christianity A.D. 100-325, “Chapter 13. Ecclesiastical Literature of the Ante-Nicene Age, and Biographical Sketches of the Church Fathers.” sec. 159-204.
§ 184. Caius of Rome.
Caius of Rome, active in the early 3rd century, wrote in Greek, but “was probably a Roman presbyter” (Schaff 2014, loc. 22349). Schaff identifies him as “an opponent of Montanism and Chiliasm.” This is known from quotations in Eusebius. Schaff acknowledges that we know very little about Caius (Schaff 2014, loc. 22359). There has been some confusion of the persons and work of Caius and Hippolytus. Schaff takes them as different but easily confused people, active at the same time.