“A Study of 17th-Century Hán-Việt Readings” is a monograph developed from Dr. Nguyễn Đại Cồ Việt’s doctoral dissertation (2011) at Peking University. Although the main text is written in Chinese, the book includes a Vietnamese introduction that systematizes its methodology and specialized terminology. The study introduces the concept of “Vietnamese readings of Chinese characters” as a framework encompassing layers of Sino–Vietnamese contact across history, and is distinguished by its theory of “internal contact,” which explains the interaction between Sino-Vietnamese and native Vietnamese phonological strata. Drawing on early Quốc ngữ sources, especially the "Annamese–Portuguese–Latin Dictionary"(1651) and "History of Annam"(1659) by the Vietnamese priest Bento Thiện, the author reconstructs the phonological system of the 17th century, identifying new patterns of correspondence as well as previously unexplained irregularities. The work emphasizes the agency of Vietnamese in the process of “Vietnamizing” external elements, while clarifying the distinction between standardized Hán-Việt readings and localized Hán-Nôm forms. It represents a significant contribution to historical phonology and to the study of Hán-Nôm materials.