Alliaria petiolata, Garlic Mustard.

Here is a link that might be useful: Google image results

thanks, should i be concerned? how do i remove them from my lawn?

These are shallowly rooted annuals, manual control is easy: just pick them when you find them. If they are in the lawn I'd think the lawnmower would do the job, I usually find them along my fenceline. They reseed like crazy, so it's important to get them before they set seed.