Sorry to hear this. BONANZA is one out of only two (old) American western shows that have become popular over here (the other being GUNSMOKE), so I obviously know very well who he was.
Norwegian press writes that he was the "last of the BONANZA stars", but they're obviously forgetting Mitch Vogel, who played young Jamie in many episodes. He's only 59, and truly the last of the "BONANZA stars" (not counting Tim Matheson, who was a regular in the last season).
David Canary was a good addition to Bonanza. His onscreen rapport with the series' stars, particularly Michael Landon, was always superb. As ofen as his character was locked up and accused of murder on that show, he should have been made an honorary Cartwright.
