The Prose Edda on Gunnar
The Younger Edda: > Chapter Iv. > The Niflungs And Gjukungs.
attestation: Gunnar and Hogne inherited Fafner's gold and the Gift of Andvare after Sigurd's death
"Gunnar and Hogne inherited Fafner's gold and the Gift of Andvare, and now ruled the lands."
attestation: Gunnar and Hogne hid Fafner's hoard in the Rhine before visiting Atle, and that gold has never been found since
"before they started on their journey they concealed Fafner's hoard in the Rhine, and that gold has never since been found."
attestation: Gold is called the Niflung treasure because Gunnar and Hogne are called Niflungs and Gjukungs
"Gunnar and Hogne are called Niflungs (Niblungs) and Gjukungs. Hence gold is called the Niflung treasure or inheritance."