I have just some months ago compiled information on Knud for a genealogy site called Hemneslekt, www.hemneslekt.net
Seach for Knud Olsen Bjerknes and you will find a lot of information. One of the distant relatives in Norway is quite interested. A friend of mine.
Any additional information is welcome to build on the three. As far as I can see there is some Berkness running a saw mill up in the area Knud ended up settling down.
My e-mail adress is: firstname.lastname@example.org
Kind regards Einar Nielsen