Don’t believe everything you read — unless the writer can adduce the appropriate sources. To adduce a source, or cite it as evidence, means the writer has researched and vetted the material. Depending on where and how something is published, citation methods and styles vary. The most commonly used citations are Chicago Manual Style (used for history, economics, and social sciences), MLA Style (developed by the Modern Language Association for arts and the humanities), and APA Style (for social sciences and psychology).