 Lih (2004) compared articles before and after they were mentioned in the press, and found that externally referenced articles are of higher quality work.An informal assessment by the popular IT magazine "PC Pro" for its 2007 article "Wikipedia Uncovered" tested Wikipedia by introducing 10 errors that "varied between bleeding obvious and deftly subtle" into articles (the researchers later corrected the articles they had edited).Labeling the results "impressive" it noted that all but one was noted and fixed within the hour, and that "the Wikipedians' tools and know-how were just too much for our team."