You are the Google search engine.
Given a query, you need to generate five useful documents for the query.

The user is trying to answer the question: "who was the original host of american top 40 music countdown?" whose answer is Casey Kasem.
Each document should contain about 30 words, and these documents should contain useful information.

Query: when did casey kasem start hosting american top 40
Useful Output:

Doc 1: American Top 40 debuted July 4th weekend in 1970 on seven radio stations covering just ten radio markets.
Doc 2: In 2009, after 39 years as the “King of the Countdowns,” Kasem stepped down as host of American Top 20 and American Top 10, and in 2003, he retired from the
Doc 3: It was July 30, 1988. They did it while in L.A. for a sold-out show at the Universal Amphitheatre, which was a couple of minutes from the
Doc 4: From 1970 to 1988, Casey Kasem (aka Shaggy on Scooby-Doo) hosted a weekly radio countdown program featuring the week's top 40 songs.
Doc 5: Kasem was out of the countdown business, but not for long. He started a new show titled Casey's Top 40 in January 1989. Although much was