MLA (Modern Language Association) style is commonly used for writing research papers and essays in the humanities, such as English, history, and philosophy. APA (American Psychological Association) style is commonly used for writing research papers and essays in the social sciences, such as psychology, sociology, and education. CMS (Chicago Manual of Style) style is commonly used for writing research papers and essays in the humanities and social sciences, but it is not as widely used as MLA and APA styles.