In a number of fields, the sources researchers work with are usually classified as either primary sources or secondary sources. (Content taken and adapted from Guidelines for Primary Source Literacy, Developed by the ACRL RBMS-SAA Joint Task Force on the Development of Guidelines for Primary Source Literacy)
Primary sources are materials in a variety of formats, created at the time under study, that serve as original evidence documenting a time period, event, people, idea, or work. Primary sources can be printed materials (such as books and ephemera), manuscript/archival materials (such as diaries or ledgers), audio/visual materials (such as recordings or films), artifacts (such as clothes or personal belongings), or born-digital materials (such as emails or digital photographs). Primary sources can be found in analog, digitized, and born-digital forms.
Primary sources can also include quantitative or qualitative data, anything that you directly analyze as first-hand evidence in support of a claim.
Works synthesizing and/or commenting on primary and/or other secondary sources. Secondary sources, which are often works of scholarship, are differentiated from primary sources by the element of critical synthesis, analysis, or commentary.
Work closely with your advisor and committee members to decide on primary sources that can help you answer or address your research question. Purdue Libraries provides students with subscription access to a variety of databases. Many of these databases contain digitized archival, historical, or data collections that may be used as primary sources in your research project.
Relevant databases can be found by visiting the Libraries' A-Z Databases list. Depending on your research project, try limiting Database Type to "Archival, Historical and Primary", or "Statistics and Data".
For a limited selection of primary sources available through Purdue Libraries, see the Primary Source Collections page on this guide.
Tip: Developing a research question based on the primary sources that are readily available to you can be a helpful time-saving strategy.