This assumes that the four liberal sources of information are independent, and not as consistent in their biases as Fox News (which is itself a composite, because there are different shows with presumably different editors).
The cited research is here. The relevant figure in on p. 22 (p. 28 of the PDF). An equally plausible description would be that Liberals use only two sources, New Yorker and Slate, whereas Conservatives get information from Breitbart, Rush Limbaugh, Blaze, Sean Hannity, and Glenn Beck.
h/t Oso Takano