German Protestant princes, led by Frederick IV of the Palatinate,
meet at Heilbronn to oppose the Holy Roman Emperor, Rudolf II.
Citation:
Editors. "The German Protestant princes meet at Heilbronn".
The Literary Encyclopedia. First published 01 February 2011
[http://www.litencyc.com/php/stopics.php?rec=true&UID=15469, accessed 19 June 2013.]