After comparing relevant documents, Prof. Nguyen Hue Chi claimed that the key to decode two royal decrees of the Yongle Emperor in Viet kieu thu and Minh thuc Iuc is the understanding of the compound word "book documents" used in these two royal decrees. By understanding completely and accurately that compound word, the authors will see nothing contradictory in the Yongle Emperor's orders: burning and destroying every cultural heritage of the Vietnamese people but seizing and keeping books of wealth, money, population and maps of districts in order to dominate the country long-lastingly.