Harvard University Press, founded in 1913 and affiliated with Harvard University, is a highly academic publishing house. Walter De Gruyter has a long history of over 260 years and is headquartered in Berlin. Its publications cover all disciplines and is a comprehensive academic publishing house. De Gruyter Press cooperates with Harvard University Press to digitize 2,785 out-of-stock and out-of-print books of Harvard University Press from 1913 to 2006 (Copyright), and provides electronic access via De Gruyter platform. Through this cooperation project, the classic works such as "The Harvard Brief Dictionary of Music" by Willi Apel; "The Bill of Rights" by Learned Hand can be reappeared for readers after many years. In addition, the list includes more than 100 classic books on Chinese history, politics, and culture. The subjects involved include history, literature, law, philosophy, social sciences, arts, religion, science, medicine, etc. Among them, the books of humanities and social science account for nearly 90%, and the science, technology and medical books account for nearly 10%. This batch of out-of-print books was exclusively distributed through the De Gruyter Press and accessed through the De Gruyter platform.