At this time of year, students are buying textbooks and looking for ways to avoid reading them. Nothing is new about that, The New York Times reports. CliffsNotes guides, with their familiar yellow and black covers, have been in book bags since 1958. What has changed is how many study guides, or cheat sheets, are available online and on mobile phones. Whether you know them as CliffsNotes, SparkNotes or Shmoop, these seemingly ubiquitous guides are now, in many cases, free. “Two to three years ago, the wisdom was that students do research online, but not study online,” said Emily Sawtell, a founder of McGraw-Hill’s online collaborative study site called GradeGuru. “That has changed in the last 12 months.” Ms. Sawtell said she had tracked a significant increase in the search term “study guide” on Google. Professors warn that these guides are no substitutes for reading great works of literature, but concede, grudgingly, that as an adjunct, they can stimulate thought and deepen insight.