* Books: Textbooks, scholarly monographs, trade books summarizing research findings.
* Journal Articles: Articles reviewing existing literature, meta-analyses combining findings from multiple studies, theoretical papers.
* Government Reports: Statistics, policy analyses, census data.
* Market Research Reports: Reports summarizing data collected by market research firms.
* Databases: Academic databases (like JSTOR, Scopus, Web of Science), statistical databases (like Statista, the World Bank data).
* News Articles: Articles summarizing research findings or reporting on relevant events (though these should be used cautiously due to potential bias).
* Websites: Government agencies, reputable organizations, and academic institutions often publish summaries of research.
Essentially, anything that summarizes, analyzes, or interprets data already collected by someone else is a source of secondary research.