Going along with the others, (and prefacing the IANAL, though I've taken classes on civil/business law and deal with some copyright issues as someone who writes software) the crux of the issue is whether or not you've "transformed" the cited copywritten work. Summarizing can be transformational by itself (I'd agree with the abovementioned 10% rule). If you're trying to provide commentary or criticism, you're even better protected, as the cornerstone of fair use is academic/critical review. So long as the article is more about "what you think about X" rather than "X" itself, you're on pretty good ground.
That's about as good as you can get. Fair use cases are decided on a case-by-case basis. Precedent doesn't necessarily help you as it's considered very narrowly. Though, again, IANAL so I might not be explaining /interpreting that correctly. Though I'm fairly certain I'm in the ballpark here. Which might not be good enough.
TL;DR: I think you're fine, but if you want to be certain consult a lawyer.