John Zápolya’s letter to Ferdinand I

The secrect covenant between John Zápolya and Ferdinand I stated that they help each other against the Ottomans, mutually retained the parts of the country they had already owned, and, after the death of Zápolya, his rival received his lands. John Zápolya’s letter to Ferdinand I about Gáspár secretary, who was sent to him in connection with the conclusion of peace.
Reference Nr.: HU MNL OL E 142 Fasc. 1. No. 15.