Many historical oeuvres are known by multiple names and/or multiple variations
of each name. For example:

- The title of Thomas Malory's *Le Morte d'Arthur* was originally written as
  *Le morte Darthur*, inaccurate Middle French for *The Death of Arthur*

- Jeoffrey of Monmouth's *Historia regum Britanniae* (en. *The History of the
  Kings of Britain)* was originally called *De gestis Britonum* (en. *On the
  Deeds of the Britons*)

- *La mule sans frein* is also known *La demoiselle a la mule* (en. *The mule
  without a bridle* and *The damsel with the mule*)

What is the way (or multiple ways) to decide which of these titles to use in
your own work when you citing, referencing, or simply discussing these works?