Primary Literature provides current /original information on which the knowledge of drugs and therapeutics is built. It can be used to validate information found in tertiary sources or provide more depth about a topic. Examples of primary literature include patents, conference papers/posters, journal articles reporting original research, case reports, clinical trial protocols,etc.
Secondary Literature provides gateways or tools to get to primary resources. Indexing and abstracting services are important composition of secondary literature. Examples of secondary resources include indexes, bibliographies and bibliographic databases such as PubMed and Embase.
Tertiary Literature presents summaries or condensed versions of known information from primary and/or secondary sources. They are convenient, usually easy to use and provide quick access to information. Examples of tertiary sources are: websites, textbooks, databases, drug compendia, review articles, encyclopedias, etc.