Excerpts from the Commentary on Peter of Spain's Tractatus
- Selections from this secondary work by Simon of Faversham, translated by John Longeway.
- http://uwp.edu/~longeway/peterspa.htm

Peter of Spain (Petrus Hispanus)
- Life and work of 13th century logician and author of the Tractatus; from the Stanford Encyclopedia by Joke Spruyt.
- http://plato.stanford.edu/entries/peter-spain/