Which kind of detail should always have a citiation in a research paper?

In a research paper, any detail that is not common knowledge or is derived from another source should always have a citation. This includes facts, statistics, theories, and direct quotes from other works. Additionally, any ideas or interpretations that are not the author's original thoughts should be properly attributed to their original sources to avoid plagiarism. Proper citation not only gives credit to original authors but also strengthens the credibility of the research.