Complex sentence: The latter problem remained open for 25 years until it was solved by Kosaburo Hashiguchi, who in 1988 published an algorithm to determine the star height of a regular language.
Split into simpler sentences: The latter problem remained open for 25 years until it was solved by Kosaburo Hashiguchi. In 1988, Hashiguchi published an algorithm to determine the star height of a regular language.