Doctorates in Australia may be research doctorates (normally titled PhDs) or professional doctorates (normally titled to refer to the field of practice, e.g. Doctor of Engineering. Professional doctorates still require research leading to "a significant and original contribution to knowledge in the context of professional practice" and should not be confused with extended master's degrees that bear similar names for historical reasons: the Juris Doctor and Doctors of Medical Practice, Physiotherapy, Dentistry and Optometry. Despite their names, these extended master's degrees may not be described as doctoral degrees nor do they confer the right to use the title of doctor on their recipients.