National Park Service Alaskan Dall Sheep Survey Units, Francis Singer, 1984
Dall sheep aerial survey units from the early 1980s by Francis Singer in Noatak National Preserve and Gates of the Arctic National Park and Preserve in Alaska. 

Dall sheep were surveyed 1981-83 in six National Parks and Preserves in Alaska by Francis Singer, National Park Service, Alaska Regional Office, Anchorage …