1. Obsidian Trade at San Lorenzo Tenochtitlan, Mexico
2. Hammond, N., Lubaantun: A Classic Maya Realm: CH8 (1975).
3. PARK, R.E., AM J SOCIOL 35: 60 (1929).
4. RENFREW, C, PROCEEDINGS OF THE PREHISSTORY SOCIETY, 1966 32: 30 (1966).
5. Stross, F. H., Lubaantun: A Classic Maya Realm: CH8 (1975).