Series of Modern Mongolian Documents . Knowledge is a series of historical materials, which is scattered in various journals, Newspaper Abstracts, memoirs and various Chinese documents related to Mongolia in various government bulletins during the 100 years from 1840 to 1949. This book covers the political, economic, military, cultural, educational, religious, historical and many other aspects of modern Mongolia. It comprehensively reflects the historical, cultural, social and economic changes and development trend of Mongolia and even the whole northern China since modern times. It has strong national and regional characteristics, large amount of information, strong instrumental role, and serves as detailed reference of modern Chinese history and modern times, history of Mongolia. It can also provide basic literature support and enhance background understanding for the establishment of "e;close, honest, beneficial and tolerant"e; neighboring state relations and construction of Belt and Road Initiative, which has realistic significance. There are about 300 thousand words in the book, which covers the political, economic, social, cultural and other aspects of Mongolia in the corresponding period. The types of travel notes included are rich. The field investigation and the literature of ancient books prove each other. The writing is beautiful, elegant and vivid.