At http://shop.oreilly.com/product/0790145305770.do?code=MSDEAL, Microsoft Press are offering the Microsoft® Manual of Style, 4th Edition as a PDF for 50% off using the MSDEAL code."Maximize the impact and precision of your message! Now in its fourth edition, the Microsoft Manual of Style
provides essential guidance to content creators, journalists, technical
writers, editors, and everyone else who writes about computer
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There is a sample chapter for free download at the above link
