Archaeologist and rock art researcher Lawrence L. Loendorf is president of Sacred Sites Research, which records and analyzes pictograph and petroglyph sites and promotes their protection. Writer and editor Nancy Medaris Stone is the coauthor, with Loendorf, of Mountain Spirit: Sheep Eater Indians of Yellowstone. Davíd Joaquín is a freelance artist and illustrator. His illustrations have appeared in Mountain Spirit: Sheep Eater Indians of Yellowstone.