Library Eusebius of Caesarea Church History
Book 3, Chapter 2: The First Successor to St. Peter in Rome.
1. After the martyrdom of Paul and of Peter, Linus was the first to obtain the episcopate of the church at Rome. Paul mentions him, when writing to Timothy from Rome, in the salutation at the end of the epistle.
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.