Editors. "By the Treaty of Gyalu, John Zápolya's widow cedes Hungary to Ferdinand". The Literary Encyclopedia. First published 01 November 2010
[http://www.litencyc.com/php/stopics.php?rec=true&UID=14660, accessed 23 May 2013.]
The Treaty of Gyalu (currently Gilau, Cluj, in Romania) is signed between John Zápolya's widow, Isabella of Poland, and Ferdinand of Austria and Bohemia. By its terms, Isabella cedes Hungary to Ferdinand.