Historiography is the study of the methods of historians in developing history as an academic discipline, and by extension is any body of historical work on a particular subject. The historiography of a specific topic covers how historians have studied that topic using particular sources, techniques, and theoretical approaches. Scholars discuss historiography by topic—such as the historiography of the United Kingdom, that of WWII, the British Empire, early Islam, and China—and different approaches and genres, such as political history and social history. Beginning in the nineteenth century, with the development of academic history, there developed a body 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.