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: "when did timbuktu become a world heritage site?" whose answer is in December 1988.
Each document should contain about 30 words, and these documents should contain useful information.

Query: when timbuktu became a world heritage site
Useful Output:

Doc 1: Designated as a World Heritage Site in 1988, Timbuktu City is regarded as the intellectual and spiritual capital of Africa's Islamic propagation in the 15th and
Doc 2: Timbuktu, which in the 15th and 16th centuries was one of Africa's leading spiritual and intellectual centres, was inscribed on the World
Doc 3: Founded in the 5th century, the economic and cultural apogee of Timbuktu came about during the15th and 16th centuries. It was an important centre for the
Doc 4: Publications World Heritage Review Series Resource Manuals World Heritage wall map More publications   More Contacts Site Map Become a member Donate Now!
Doc 5: It was, in fact, a major trading and Islamic intellectual centre in the 15th and 16th centuries. Situated on the southern fringe of the Sahara desert in Mali