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: "The city of Gavle received its charter during which era?" whose answer is era of the Kalmar Union.
Each document should contain about 30 words, and these documents should contain useful information.

Query: when did Gavle receive its charter
Useful Output:

Doc 1: Gävle is first mentioned as a town in official history books in the year 1413 but only received its official town charters in the year 1446.
Doc 2: Gävle is first mentioned as a town in official history books in the year 1413 but only received its official town charters in the year 1446.
Doc 3: Find local businesses, view maps and get driving directions in Google Maps.
Doc 4: It is the oldest city in the historical Norrland, having received its charter in 1446 from Christopher of Bavaria. Thanks, I learned
Doc 5:  received its charter in 1446 from Christopher of Bavaria. However, Gävle is far nearer to the greater Stockholm region than it is to most