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: "In what century did Olaf Geirstad-Alf  and Halfdan the Black live in?" whose answer is ninth-century.
Each document should contain about 30 words, and these documents should contain useful information.

Query: Halfdan the Black reign
Useful Output:

Doc 1: Apparently, the head was entombed at Hringaríki, while three other sections of Hálfdan's body were buried at Raumaríki, Vestfold and Heithmork.
Doc 2: The oldest text referring to a “king of Norway” is an inscription by the king Harald Gormsson during his reign between the years 958-987.
Doc 3: Harald Fairhair's father, Halfdan the Black, was a petty king in the regions of Vestfold and Oppland. Legend has it that Harald was only ten
Doc 4: Halfdan the black this week, an interesting character for sure with in my opinion a completely unnecessary death just to try and prove a point about Ubbe and
Doc 5: Harald (1) was but ten years old when he succeeded his father (Halfdan the Black). He became a stout, strong, and comely man, and withal prudent and manly. His