I've studied it for years, and I'm still not sure I understand it.

WSJ: Angelina Jolie as Film Director, Promoter

"I'm not sure I understand why new-media companies need to pay to get big companies to pay attention to them, " says Dave L. Balter, founder of BzzAgent, a word-of-mouth marketer that Puris approached about joining up.

FORBES: Magazine Article

I'm not sure -- there have been a variety of amendments, as I understand, voted on -- some of them defeated, like I think -- according to Dana Milbank, columnist for The Washington Post, and I'm just citing him -- 35 votes now by Republicans to repeal the Affordable Care Act.

WHITEHOUSE: Press Briefing

Mr. ANNAN: And I think we need to be able to take care of the concerns of Israel, and I understand the issue of rearmament that we need to make sure that arms do not come in either through the airports and the borders or through the seaports.

NPR: Annan Works Both Sides of Hezbollah-Israel Conflict

And we want to make sure that we're not getting too far ahead of ourselves in terms of targets, even as I understand that the science compels us to move as rapidly as we can.

WHITEHOUSE: President Obama at Copenhagen Climate Change Conference

So I understand why people would say, boy, this is -- I'm not so sure about this -- even though they know that what they got isn't working.

WHITEHOUSE: "White House to Main Street" Town Hall: Elyria, OH