The reason we don't have to multiply by two in the solution is because we are drawing from the same pool. In the example you are thinking (http://gmatclub.com/forum/john-has-on-his-shelf-four-books-of-poetry-145499.html
), there are two different pools to choose from, novels and reference. In this case, the only pool we're picking from is the pool of women. Of the two picks, we want the first to be a woman, and the second to be a woman. There is no way to "flip" this selection, as the "flip" is the same as our original scenario. In the other problem, the reason we have to multiply by two is because we have two outcomes, the first selection is a novel and the second is a reference, or the first is a reference and the second is a novel.
Hope this makes sense!
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