CliffsNotes is the original (and most widely imitated) study guide. CliffsNotes study guides are written by real teachers and professors, so no matter what you're studying, CliffsNotes can ease your homework headaches and help you score high on exams. Founded in 1958 by Clifton Keith Hillegass, CliffsNotes is the original company that produced study guides and book summaries ranging from Shakespeare to Algebra and the SAT!