1. Locke, L. L., Amer. Anthropol., 14, 325 (1912).
2. Nordenskiöld, E., Comparative Ethnological Studies, 6, part 1, 2 (1925).
3. Antiquity, 40 (1966).
4. Day, C. L., Quipus and Witches Knots (University of Kansas, Lawrence, 1967).
5. Locke, L. L., The Ancient Quipu or Peruvian Knot Record, 43 (Amer. Mus. Nat. Hist., New York, 1923).