Identify this weed?

My yard has seen an amazing turnaround in just the last year. The past 2 years I was complaining about almost 100% crabgrass coverage. I took it very seriously, and now I can only find the occasional crabgrass plant. I powerseeded in the fall, and was meticulous in my usage of pre-emergent crabgrass preventer. The powerseeded grass came up thick and lush, effectively choking up most crabgrass.
But I digress...
The one weed I had last year that seems to have come back is the one in the following pictures...
http://www.bookac.com/Images/Lawn/weed1.jpg
http://www.bookac.com/Images/Lawn/weed2.jpg
This weed seems to grow in packs, in small sections of my front yard. It is not deeply rooted, and is easy to pull. Can anyone identify it, so I can treat it properly? It grows really high, about twice the rate of my grass, so it sticks out after 4-5 days after mowing.
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wrote:

It's nutgrass and very difficult to get rid of. If you pull it out, make sure you do it in softened soil, well watered and get the whole nutlet, any rootlets and any stolons or it will be back in ten minutes. I believe only one thing on the market is recommended for it, and that's called Image. I'm not sure IT works that well.
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What you said about pulling it out makes sense. Seems no matter how much I pull, it always comes back.
Thanks for your response.

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Is this IMAGE product safe for use on a standard fescue blend lawn like mine? Does it kill grass too?

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I actually don't know, as I've never used it. It is not organic, or natural. I'm sure you can look it up and get all the indications.
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