Telemark, Norway Municipalities

My father's ancestors emigrated to the United States from Telemark, Norway.
I have several municipality or parish citations using the following names:
Heddal, Hitterdal, Hitterdals, Hjertdals. I also have one map of Telemark,

Jan...

At least two of these are different parishes:
Heddal, near Notodden; Hjartdal, further west (up) the valley, between
Notodden and Seljord.
Hitterdal and Hitterdals seem to be one and the same name; the -s
being a genitive (e.g. Hitterdals Sogn meaning the parish of
Hitterdal). I thought Hitterdal was in another part of the country
(Sør-Trøndelag), but obviously also in Vinje municipality in Telemark.

posted on the Johan Borgos website. On it there is only one municipality
with a similar spelling. Could this multiplicity of names be alternative
spellings of the same name, perhaps demonstrating changes over time? If so,
should I leave them as is, or should I consolidate them? If I consolidate,
would using the most current spelling facilitate or hinder research?

I'm a neophyte. You're help will be gratefully received.

Hugh Watkins...

amost certainly yes

but better ask the locals who really know how the language has evolved

The Genealogy Society of Norway - DIS (Norwegian name: "DIS-Norge") was
founded January 12, 1990. There are about 8000 members (2006) and the
membership increases daily. The main goal of the association is to
create a common forum for persons interested in using computers as a
tool in genealogical research in Norway. DIS-Norge wants to spread
knowledge about and at the same time stimulate genealogical research. We
have good relations with similar associations in the Nordic countries
and are continually exchanging experiences. We facilitate contact
between genealogists in Norway, both electronically and face to face. In
the case of local interest, we try actively to begin new local
organisations.

We want to offer interesting services for English speaking users and
members too! For the time being you may find that some of these services
may be helpful (in some cases you need to click an English flag or an
"English" link to select English language)

<< do gte in the habit of posting examples of

date name event place
and OCCUPATION
the last is important with so many similar patronymic last names derived
from about 15 popular first names

Hugh W