"some have rejected the Epistle to the Hebrews, saying that it is disputed by the church of Rome, on the ground that it was not written by Paul." Eusebius, Hist. Eccl. 3.3.5 (text); cf. also 6.20.3 (text).
crivoice.org
Hahn, Roger. "The Book of Hebrews". Christian Resource Institute. [2] Accessed 17 Mar 2013]
Duling, C. Dennis (2003). The New Testament : history, literature, and social context (4th ed.). Belmont, CA: Thomson/Wadsworth. p. 281. ISBN0155078569. OCLC52302160.