Promotion and EducationalServices Carl W. Harmon, Jr., Jerome F. Owecke, F. William Rath, Robert J. Warfel, Towne Windom. 구매 로버트 G. 코리, 토마스 L. 플레처, 쉴라 H. 이멜. Translation Zbigniew Jan Lutyk COPYRIGHT National Geographic Society, th and M Sts.