Your professor may require you to find scholarly sources popular sources, secondary sources or primary sources on your topic. Here's a very basic guide if you need more details:
Primary Sources: Primary sources are the raw stuff of history. Examples of primary sources:
Some Primary Sources are also known as popular sources.
Secondary or Scholarly Sources:
These are the peer reviewed articles and scholarly books that historians write after they have worked with the primary sources -- and consulted other secondary articles or books.
Historiography
Historiography is the study of how historians have interpreted historical events throughout time. The student of the historiography of Algiers, for example, might want to compare how the country was seen by historians during the colonial era and afterthis One way of doing this comparative interpretation, is by looking for bibliographies on a subject or using the keyword "historiography" combined with "Algiers" subject of your research in Historical Abstracts, in the Library Search or Academic Search Premier. -- or simply typing in Algiers and limiting by date.
