hi -
the more general version of this advice is that you can improve your RC skills through basically
any source that is scholarly, FORMAL, and well written. if the articles satisfy those three criteria - and if they're the approximate length of gmat passages (i.e., not too long) - then they should give you good practice.
you may also want to read some more business-specific things. you could try googling "online business journal" and seeing what you get. here's one example:
http://www.mckinseyquarterly.com/home.aspxthis would be useful, especially in light of the fact that EVERY gmat contains at least 1-2 passages whose content is directly related to business.
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whenever you read these articles, make sure that you can do the following:
* summarize the MAIN POINT, in 1-2 sentences.
* explain WHAT THE AUTHOR IS DOING in the article.
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the problem, of course, is that you can read as many of these articles as you want and still not necessarily get any practice on answering actual gmat QUESTIONS (which have an annoying, non-intuitive format).
one thing you could try is the reverse: you could pretend that your job is to WRITE questions.
take the article and write 4-5 questions about it, along with correct answers (and possibly wrong answers, too)
* main idea questions
* author's purpose questions ("why does the author use the word ______ here?")
* inference questions ("what else do we know from this statement?")
* detail questions ("according to the passage, ...")
this is not easy to do, but it's a good start.
good luck