Sacra Propediem §7

⁷ Uncontested founder of the Third Order, as he was of the two first, Francis was for it, further, without doubt, the most wise legislator. We know that for this work he had the precious aid of Cardinal Ugolino, who later, under the name of Gregory IX, was to make illustrious this Apostolic See, and who, after having whilst he lived, maintained the closest relations with the Partiarch of Assisi, elevated later on his tomb a magnificent and sumptuous basilica. As to the rule of the Tertiaries, no one is ignorant that it was regularly approved by Our predecessor, Nicholas IV.