There are forums, mailing lists, and facebook groups for almost any group with shared ancestry and the people who populate them can be amazingly helpful. So here is how I solved a mystery with assistance from various Norwegian helpers.
I have recently been working on the ancestors of my g-grandfather H. H. Lee (originally Hans or Halvor Skjold) from Etne, Hordaland, Norway since I have so many new relatives from his families found with DNA testing. When last in Salt Lake City, I photographed numerous pages of farm entries from the Etnesogas at the family history library and took several of his lines much further back. See the chart below (from wikitree) for those annoying blank spots I wanted to fill in.
I found the ancestors of Ingeborg Haktorsdtr, one blank spot below, in the Holmedal books. But my 3rd great grandfather Øystein Gabrielsen Bjørgjo evaded me. He appeared as if by magic on the Bjørgjo farm with no clue as to his origins. I tried the online Norwegian archives with no success, perhaps because they are a bit difficult for us English speakers. So I decided to ask for help.