Schaff, Philip. "Ch. 30: The Apostolical Church Order, or the Ecclesiastical Canons of the Holy Apostles." The Oldest Church Manual Called the Teaching of the Twelve Apostles. Second Edition, Revised and Enlarged. New York: Funk & Wagnalls, 1886, 127-132.
Scholarly opinion considering "the Pseudo-Clementine Apostolical Constitutions and Canons" has long assumed an older and simpler source document (Schaff 1886, 128). Schaff sees this in the Didache, but with another intermediate document, variously known as "Apostolical Church Order, or Ecclesiastical Constitutions and Canons of the Apostles, also quoted as Epitome, or Apostolical Canons" (Schaff 1886, 128). This was discovered and published in the late 1600s, and again in the mid 1800s (Schaff 1886, 128-129). Of interest to Schaff is the fact that this document represents parts of Didache 1-6 as dialogue spoken by the various aplstles (Schaff 1886, 130). Schaff summarizes Harnack's opinion that "the Apostolical Church Order is a mechanical and unskillful compilation of four or five oler documents, the Didache, the Epistle of Barnabas, and two other writings, one from the end of the second, the other from the beginning of the third century" (Schaff 1886, 132).