Editors. "The archdukes aim to keep the imperial crown Habsburg". The Literary Encyclopedia. First published 01 February 2011
[http://www.litencyc.com/php/stopics.php?rec=true&UID=15702, accessed 19 June 2013.]
Archdukes Matthias and Maximilian, brothers of Holy Roman Emperor Rudolf II, undertake to prevent the imperial crown from leaving the House of Habsburg.