Lots to look at! Thank you all. My interests are specific to difference equations right now but I realize that I have missed a lot by not looking at the subject more carefully so I wanted something more formal than just looking at topics on the internet. Yes, I am looking for completely legal. For right now I am looking for free downloadable e-books. I'm not sure when I can get up a decent amount of money for a book. I will look at your list, Plato, for used copies. Thanks again! -Dan