↑ Lehmkuhl, Augustinus. "Moral Theology." The Catholic Encyclopedia. Vol. 14. New York: Robert Appleton Company, 1912. 26 May 2019 <http://www.newadvent.org/cathen/14601a.htm>.
↑ Bernhard Häring, Free and faithful in Christ. Moral Theology for priests and laity, I/General Moral Theology. For freedom Christ has set us free (Gal 5,1), Slough 1978, focus on chapter 3
↑ Ratzinger, Joseph Cardinal (Pope Benedict XVI). Introduction To Christianity, 2nd Edition (Communio Books) (Kindle Locations 304-306). Ignatius Press.
