Does the New York Times fact-check its editorial pages? A slew of recent errors in Times opinion pieces suggest it does not - or, if it does, that it needs to do a better job.

The most recent bout of falsehoods was, perhaps unsurprisingly, directed at the much-maligned owners of Koch Industries, Charles and David Koch. In a Sunday, April 3 op-ed in the Times, David Callahan, a senior fellow at the left-wing advocacy group Demos, made numerous factual errors regarding the company and its fraternal owners, and about non-profit tax law - together, the two central topics of his piece.

Koch Industries sent a letter to Andrew Rosenthal, the Times's editorial page editor, on Tuesday requesting corrections to the "several errors" in Callahan's op-ed, but as of Monday afternoon, no correction had been issued. Read the full letter below the break.