Your instructor may want you to use scholarly (or "peer-reviewed") sources. What does this mean?
There are two main types of scholarly sources:
Popular sources, on the other hand, are intended for the general public. These sources are more introductory, may not be written by experts in a field, and often do not cite any other sources. Examples of popular magazines include National Geographic, The Economist, Time, Newsweek, and People.
How can you tell if an article or book is scholarly? Look for:
Using keywords some examples:
Using ancient egypt in library catalogs and data bases will retrieve any record that contains these three words.
Use quotation marks to retrieve only relevant records: "ancient egypt"
Truncating words using an asterisk will retrieve more related records: egypt* will retrieve egypt, egypt's and egyptian
Use broad terms for finding encyclopedias, bibliographies, general history of a country, indexes: encyclopedia* ancient egypt"
Use focused terms when searching for articles or books related to your topic: tomb* thoth