Reference Library. Svizzero, S.; Tisdell, C. The Persistence of Hunting and Gathering Economies. Social Evolution & History. 2015, 14 [2020-07-11]. (原始内容存档于2021-04-22)
(页面存档备份,存于互联网档案馆), p. 2. Redacted text includes the names of living intelligence sources, intelligencegathering methods still used today and not commonly known, and