You will be given a definition of a task first, then an example. Follow the example to solve a new instance of the task.
Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.

In 1582 the united provinces invited francis, duke of anjou to lead them; but after a failed attempt to take antwerp in 1583, the duke left the netherlands again. after the assassination of william of orange (10 july 1584), both henry iii of france and elizabeth i of england declined the offer of sovereignty. however, the latter agreed to turn the united provinces into a protectorate of england (treaty of nonsuch, 1585), and sent the earl of leicester as governor-general. this was unsuccessful and in 1588 the provinces became a confederacy. the union of utrecht is regarded as the foundation of the republic of the seven united provinces, which was not recognized by the spanish empire until the peace of westphalia in 1648.
Solution: In what year did francis, duke of anjou leave the netherlands?
Why? The generated question is perfect. Because the question is based on second sentence of the input passage and its answer is 1583.

New input: Restless Legs Syndrome (RLS) or Willis-Ekbom Disease (WED) is highly prevalent, but patients and healthcare providers alike know little about it. Furthermore, controversy persists as to the best way of diagnosing this nosological entity. To verify whether the term used to refer to this disease entity (Restless Legs Syndrome or Willis-Ekbom Disease) affects the prevalence of self-diagnosed RLS/WED in a sample of newly graduated physicians. Newly graduated physicians were asked to self-evaluate for the presence of RLS/WED. Briefly, participants were allocated randomly across two groups. One was asked to self-assess for RLS, while the other was asked to self-assess for WED. The evaluation form given to one group asked 'Do you have Restless Legs Syndrome?' whereas the form given to participants in the other group asked 'Do you have Willis-Ekbom Disease?'. Both forms also contained the four criteria for diagnosing RLS proposed by the International Restless Legs Syndrome Study Group (IRLSSG) and instructions for self-diagnosis according to these criteria. The study sample comprised 1413 newly graduated physicians. Of the 708 participants who were given the form that used the term RLS, 87 (12.28%) diagnosed themselves with the condition. Conversely, of 705 physicians given the form with the term WED, 13 (1.84%) diagnosed themselves with the condition (p<0.0001). A greater proportion of newly graduated physicians diagnosed themselves with RLS/WED when presented with the term Restless Legs Syndrome than when presented with the term Willis-Ekbom Disease. This suggests that the term Restless Legs Syndrome may not be the most appropriate term to denote this nosological entity.
Solution:
Willis-Ekbom disease is also known as?