Historiography is the study of the methods used by historians in developing history as an academic discipline. By extension, the term historiography is any body of historical work on a particular subject. The historiography of a specific topic covers how historians have studied that topic by using particular sources, techniques of research, and theoretical approaches to the interpretation of documentary sources. Scholars discuss historiography by topic—such as the historiography of the United Kingdom, of WWII, of the pre-Columbian Americas, of early Islam, and of China—and different approaches to the work and the genres of history, such as political history and social history. Beginning in the nineteenth century, the development of academic history produced a great corpus of historiographic literature. The extent to which historians are influenced by their own groups and loyalties—such as to their nation state—remains a debated question.