This one works a little better on recycled papers than it does on Internet papers, at least in some cases, but a good sign of a plagiarized paper is that all the references in the Works Cited are at least five or ten years old. Using periodical literature which is consistently three or four years old is another giveaway. However note that commercial sites will use current sources, as recent as one month prior to ordering. General references are to other countries and examples come from newspapers, magazines, and news stories that are not common locally. In Canada, consistent references to examples from one country-like the US or Hong Kong or Taiwan or Iran that are backed up by sources from those countries may be a warning sign.
Solutions Consider requiring students to keep portfolios.
Keep samples of in-class writing and announce that these are for a comparative sample. Hold one or more in-office interviews during stages of the essay. Require drafts be submitted with the final edited copy. Ask the student to produce a Xerox or printing of the sources. Avoid open-ended or general topic choice.