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: Olaf Geirstad-Alf reign
Useful Output:

Doc 1: Olaf played an important part in the often forcible, on pain of torture or death, conversion of the Norse to Christianity.
Doc 2: Olaf Geirstad-Alf was a prominent figure in Norwegian history during the early medieval period. He is known for being one of the earliest recorded rulers of the
Doc 3: Olaf Geirstad-Alf, was a legendary Norwegian king of the House of Yngling from the Ynglinga saga. He was the son of Gudrød the Hunter and the brother of
Doc 4: Olaf Gudrodsson "Geirstad-Alf" of Yngling "King of Jutland and Vestfolk","Olaf Godfreysson","semi-legendary petty king in Norway" 780-874
Doc 5: Olaf Gudrødsson (c. 810 – c. 860), known after his death as Olaf Geirstad-Alf "Olaf, Elf of Geirstad" (Old Norse Ólaf Geirstaða Álfr), was a