Aztec land in 1519, they found that the Aztecs kept books both in temples and in libraries associated to palaces such as that of Moctezuma. For example, besides the testimony of Bernal Díaz quoted above, the conquistador Juan Cano describes some of the books to be found at the library of Moctezuma, dealing with religion, genealogies, government, and geography, lamenting their destruction at the hands of the Spaniards, for such books were essential for the government and policy of indigenous nations. Further loss was caused by Catholic priests, who destroyed many of the surviving manuscripts during the early colonial period, burning them because they considered them idolatric. The large extant body of manuscripts that did survive can now be found in museums, archives, and private collections. There has been considerable scholarly work on individual codices as well as the daunting task of classification and description. A major publication project by scholars of Mesoamerican ethnohistory was brought to fruition in the 1970s: volume 14 of the Handbook of Middle American Indians, Guide to Ethnohistorical Sources: Part Three is devoted to Middle American pictorial manuscripts, including numerous reproductions of single pages of important pictorials. This volume includes John B. Glass and Donald Robertson's survey and catalogue of Mesoamerican pictorials, comprising 434 entries, of which a considerable part proceed from the Valley of Mexico. Three Aztec codices have been considered as being possibly pre-Hispanic: Codex Borbonicus, the Matrícula de Tributos and the Codex Boturini. According to Robertson, no pre-Conquest examples of Aztec codices survived, for he considered the Codex Borbonicus and the Codex Boturini as displaying limited elements of European influence, such as the space apparently left to add Spanish glosses for calendric names in the Codex Borbonicus and some stylistic elements of trees in Codex Boturini. Similarly, the Matrícula de Tributos seems to imitate European paper proportions, rather than native ones. However, Robertson's views, which equated Mixtec and Aztec style, have been contested by Elizabeth-Hill Boone, who considered a more naturalistic quality of the Aztec pictorial school. Thus, the chronological situation of these manuscripts is still disputed, with some scholars being in favour of them being prehispanic, and some against. Classification The types of information in manuscripts fall into several categories: calendrical, historical, genealogical, cartographic, economic/tribute, economic/census and cadastral, and economic/property plans. A census of 434 pictorial manuscripts of all of Mesoamerica gives information on the title, synonyms, location, history, publication status,