Columbia subject headings:
Geomagnetism--Montana--Flathead County--Maps.
Geomagnetism--Montana--Lincoln County--Maps.
Maps.
Harvard subject headings:
Flathead County (Mont.)--Maps.
Geomagnetism--Montana--Flathead County--Maps.
Geomagnetism--Montana--Lincoln County--Maps.
Lincoln County (Mont.)--Maps.
Princeton subject headings:
Geomagnetism.
Maps.
McGregor Lake Region (Mont.)--Maps.