David McCullough (2011). “David McCullough Great Moments in History E-book Box Set: 1776, The Johnstown Flood, Path Between the Seas, The Great Bridge, The Course of Human Events”, p.101, Simon and Schuster
William Penn (1830). “The Sandy Foundation Shaken; Or, Those ... Doctrines of One God Subsisting in Three Distinct and Separate Persons, the Impossibility of God's Pardoning Sinners Without a Plenary Satisfaction, the Justification of Impure Persons by an Imputative Righteousness, Refuted from the Authority of Scripture Testimonies and Right Reason, Etc”, p.6