Schaff, Philip. "Document III: Barnabas." Oldest Church Manual Called the Teaching of the Twelve Apostles. Second Edition, Revised and Enlarged. New York: Funk & Wagnalls, 1886, 227-232.
Schaff observes that the Epistle of Barnabas "has an appendix of four chapters not found in the old Latin version, and regarded by some as spurious" (Schaff 1886, 227). In that appendix, chapters 18-20 have some similarity to the Two Ways portion of the Didache. Schaff also notes that eschatological material in chapter four resembles that of Didache 16).
The Greek style is not smooth and suggests the material was borrowed clumsily from another source.
Schaff continues with text and translation of the similar portions.