Finkelman, Paul. Encyclopedia of the United States in the Nineteenth Century (Charles Scribner's Sons, 2001), p. 270: "Once the Constitution had been ratified, Congress passed a slightly modified version of the Northwest Ordinance on 7 August 1789, since all nontreaty statutory enactments under the Articles of Confederation lapsed with the adoption of the Constitution."
Tillson, Albert. Accommodating Revolutions: Virginia's Northern Neck in an Era of Transformations, 1760-1810, pp. 142, 341 n.134 (University of Virginia Press, 2010).