1. de Gómara Francisco López Cortés. The life of the conqueror by bis secretary (Berkeley and Los Angeles, 1966).
2. von Humboldt Alexander Ensayo politico sobre el reino de la Nueva España (Mexico, 1966), (book 4, ch. 11).
3. Agricola Georgius De re metallica (Basle, 1556), Eng. trans. Herbert Clark Hoover and Lou Henry Hoover (London, 1912).
4. Altman Ida and James Lockhart (eds.), Provinces of early Mexico (Berkeley and Los Angeles, 1976).
5. Brading D. A. Miners and merchants in Bourbon Mexico, 1763–1810 (Cambridge, 1971).