Traditional encyclopedias' reliability, on their side, stand upon authorship and associated professional expertise. Many academics, teachers, and journalists rejected and continue to reject open, crowd sourced encyclopedias, especially Wikipedia, as a reliable source of information, and Wikipedia is itself not a reliable source according to its own standards because of its openly editable and anonymous crowdsourcing model. A study by "Nature" in 2005 found that Wikipedia's science articles were roughly comparable in accuracy to those of "Encyclopædia Britannica", containing the same number of serious errors and about 1/3 more minor factual inaccuracies, but that Wikipedia's writing tended to be confusing and less readable. "Encyclopædia Britannica" rejected the study's conclusions, deeming the study fatally flawed. As of February 2014, Wikipedia had 18 billion page views and nearly 500 million unique visitors each month. Critics argue Wikipedia exhibits systemic bias.