Bentdahl, Bentdahlen and Blenshen are not surnames -- those are addresses; sometimes used as additional identifiers.
You appear to be looking for persons from Dovre, Oppland which was earlier included as part of Lesja, Oppland.
See here is the birth/baptismal record for Jørgen Poulsen --
left hand page, sixth baptism (døbt) on that page.http://www.arkivverket.no/URN:kb_read?idx_kildeid=9237&i...
Online study material to learn about Norwegian naming practices and patterns:http://homepages.rootsweb.ancestry.com/~norway/na12.htmlhttp://www.nndata.no/home/jborgos/names.htmhttp://www.norwayheritage.com/norwegian-names.htmhttp://www.nndata.no/home/jborgos/farms.htm