e/Star height problem

Information
has gloss	eng: The star height problem in formal language theory is the question whether all regular languages can be expressed using regular expressions of limited star height, i.e. with a limited nesting depth of Kleene stars. Specifically, is a nesting depth of more than 2 required? If so, is there an algorithm to determine how many are required?
lexicalization	eng: star height problem
instance of	e/Formal language