Editors. "John Sigismund Zapolya of Transylvania signs a secret treaty with Maximilian II". The Literary Encyclopedia. First published 01 February 2011
[http://www.litencyc.com/php/stopics.php?rec=true&UID=15110, accessed 20 April 2014.]
A secret treaty is signed at Speyer by the King of Transylvania, John Sigismund Zapolya, and Holy Roman Emperor Maximilian II. By this treaty, Zapolya gains his goal of independence from the Sultan of Turkey, but in return renounces his Hungarian territory to the Empire.