Dead end...John Olsen Aasen.

Hello all. I'm decedent of John Olsen on the Aasen Farm (Gn 36, Bn 8). The Hitterdal Bygdenbok has little information about where he came from and who his parents are. I do have naturalization papers. They tell me that John Olsen's wife is Thone Olsdtr (which I have confirmed looking at land records). His papers also say he is from Sauer. But when I looked up Sauer in the Bygdebok I have hit a dead end. The are plenty of Ole and Johns on that farm, but no John Olsen with the birth around 1815. Are there other places I can look? Thanks in advance! Heidi