I have an infestation of this plant in my flower beds and it's now
spilling over into my lawn. I need to eradicate it, but would like to
identify it so I use the right method. I've surfed the web for common
weeds, and I can't find anything exactly like this.

Photo:
http://www.camfriends.org/users/clintp/weed.jpg

I'm in the Detroit area. The plant is about 2-3 inches tall and grows
in a dense and spreading cluster. Each 3-leaf cluster grows from an
individual stem that goes into the ground. It seems to thrive in sun
or shade, and spreads very very quickly.

The leaves *look* like parsley, but the rest of the plant has no
similarities at all. The plant itself looks like clover, but the
leaves are wrong.

Thank you!