I could understand for the older books, but the for the newer stuff, like the server 2012 pocket consultant, I don't see any button either.
Would love to buy ebooks for my entire library of the hardcover books that I have been lugging around for the past several years every time I move. they are heavy and don't store well...
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I have taken care of the issue with Windows Server 2012 Pocket Consultant, and the upgrade button should appear in a few hours. If you will give me the titles of the other books that you noticed don't have upgrade buttons, I will look into the problem.
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