Ancient Northern Sources

Saxo Grammaticus' Gesta Danorum preserves the tales of Amleth, retold in Shakespeare's Hamlet, and of Hadding, retold in Poul Anderson's War Of The Gods.

Snorri Sturluson's Heimskringla contains the Ynglinga saga and the Saga of Harald Hardrada, the latter retold in Anderson's The Last Viking Trilogy, and ends its story of Swedish and Norwegian kings in 1184.

Anderson also retold Hrolf Kraki's Saga and the story of Gunnhild, Mother of Kings. Anderson's The Broken Sword continues a story begun in the Elder Edda and a saga. See here.

Thus, heroic fantasy and historical fiction share sources and blend into a single narrative.