What does ØKB stand for (Norwegian source title)?

[mikjall77]

I am doing some research with trees found on some Norwegian websites and keep finding this as a source. It only gives it in a title with a number and side (i.e. ØKB nr. 3, side 93) mainly for birth and christening.

Being Norway and the area (parish) that I'm looking at, I am assuming that it could be Øyer Kirkebøker (Øyer Churchbook) or possibly Øyer Kirkebøker Bergen but I haven't been able to match anything up.

Is my thinking correct or does someone have another idea? Thank you!