Denifle, Heinrich, Luther and Lutherdom, vol.1, part 1, tr. from 2nd rev. ed. of German by Raymund Volz, Somerset, England: Torch Press, 1917, (Cornell University Library 2009), , p. 305. Denifle cites Luther’s Sämtliche Werke (Vols 4-6 in 1), Erlangen-Frankfurt edition, 1865, Heyder & Zimmer, vol. vi, p. 401https://en.wikiquote.org/wiki/Martin_Luther