Snyder, Gerald S. In the footsteps of Lewis and Clark, [electronic resource] / by Gerald S. Snyder. Photos. by Dick Durrance II. Illustrated by Richard Schlecht. Foreword by Donald Jackson. Produced by the Special Publications Division.. — Washington, : National Geographic Society, [1970]. — 215 p. : illus. (part col.), facsims., maps, col. ports. 27 cm. — (National geographic special publications).