OWL - The Purdue Online Writing Lab
Target Audience: High School and College Students
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This free and navigable site is useful not only for people with English as a second language, but could also benefit someone taking an English course, looking for a job, or writing professionally. For those looking for proper citation instructions, this free site has many useful tools included guides in formatting (APA, MLA, etc.) and an example paper in the chosen format. The site has resources about avoiding plagiarism, developing a resume, and more.
Link: https://owl.english.purdue.edu/