Library Eusebius of Caesarea Church History
Book 6
Chapter 6: Clement of Alexandria
Clement having succeeded Pantænus, had charge at that time of the catechetical instruction in Alexandria, so that Origen also, while still a boy, was one of his pupils. In the first book of the work called Stromata, which Clement wrote, he gives a chronological table, bringing events down to the death of Commodus. So it is evident that that work was written during the reign of Severus, whose times we are now recording.
English translation by Arthur Cushman McGiffert, in Nicene and Post-Nicene Fathers, Series II, Vol. I (eds. Philip Schaff and Henry Wace; Buffalo: Christian Literature Publishing Co., 1890). Public domain. Digital text via New Advent Church Fathers.