Instructions: In this task, you're given a passage, further information available on a particular linked term from the statement, and a question. Your job is to generate the answer to the question by using the information provided. If there is no clear answer obtainable, output 'none'.
Input: Passage: Moore started writing for British underground and alternative fanzines in the late 1970s before achieving success publishing comic strips in such magazines as 2000 AD and Warrior. He was subsequently picked up by the American DC Comics, and as "the first comics writer living in Britain to do prominent work in America", he worked on major characters such as Batman () and Superman (), substantially developed the character Swamp Thing, and penned original titles such as Watchmen. During that decade, Moore helped to bring about greater social respectability for comics in the United States and United Kingdom. He prefers the term "comic" to "graphic novel". In the late 1980s and early 1990s he left the comic industry mainstream and went independent for a while, working on experimental work such as the epic From Hell and the prose novel Voice of the Fire. He subsequently returned to the mainstream later in the 1990s, working for Image Comics, before developing America's Best Comics, an imprint through which he published works such as The League of Extraordinary Gentlemen and the occult-based Promethea. In 2016, he published Jerusalem: a 1266-page experimental novel set in his hometown of Northampton, UK.
 Link Information: none Question: How many years did Alan Moore work at DC Comics?
Output:
Answer: none