Wiktionary
historical method
n. (context historiography English) The techniques and guidelines by which historians use primary sources and other evidence to research and then to write history.
Wikipedia
Historical method
Historical method comprises the techniques and guidelines by which historians use primary sources and other evidence, including the evidence of archaeology, to research and then to write histories in the form of accounts of the past. The question of the nature, and even the possibility, of a sound historical method is raised in the philosophy of history as a question of epistemology. The study of historical method and of different ways of writing history is known as historiography.