Rudolf, 1858–89, Austrian archduke, crown prince of Austria and Hungary; only son of Emperor Francis Joseph and Empress Elizabeth. Upon his mysterious death at Mayerling near Vienna (officially declared a double suicide with his mistress, Baroness Maria Vetsera), his cousin Francis Ferdinand became heir to the Austro-Hungarian throne.
"Rudolf." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (September 21, 2018). http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/rudolf
"Rudolf." The Columbia Encyclopedia, 6th ed.. . Retrieved September 21, 2018 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/rudolf