Mark Greengrass και Michael Leslie (επιμ.): Samuel Hartlib and Universal Reformation: Studies in Intellectual Communication, 2002, σελ. 47 - Google Books
Michael Sudduth: The Reformed Objection to Natural Theology, 2009, σελ. 22 - Google Books
Mark Greengrass & Michael Leslie (επιμ.): Samuel Hartlib and Universal Reformation: Studies in Intellectual Communication, 2002, σελ. 46 - Google Books.