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I had the targus stylus but gave it away, I saw that targus released a stylus 2 in 1 so I bought that. It works just as well as the original targus stylus but I like the ability of having a pen too. 29.99 is pretty hefty but I think it's worth it b/c I use my iPad so much in class. I like penultimate, it's really good for my organic chemistry and physics classes.
the link for the 2 in 1 targus is here
http://www.bestbuy.com/site/Targus+...0411&skuId=2128179&st=targus stylus&cp=1&lp=6
 
The best ones for studying allow you to see each individual page in a preview before opening. In noteshelf I think (and penultimate), you open a book and it goes to the last page you looked at therefore if your at page 18 and you want to see what you wrote on page 6 you have to go back several pages (if that makes sense).
 
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