Primary sources include information that is obtained first-hand, such as first-hand accounts or observations. Creative works, historical documents, or first-hand accounts of research studies or data are also primary sources. Most of the time, your literature review paper or portion of your journal article should use primary sources for the most part. In contrast, secondary sources contain information about these historical documents, creative works, or research studies. Books are typically secondary sources. Tertiary sources index, abstract, organize, compile, or digest other sources. Encyclopedias or test indexes are tertiary sources.