In looking on the internet for methods of eradication I sstubled upon this thread:
Note that this thread spans 10 years! Clearly an ongoing problem. What I get from it is DON'T till as you'll be turning up old dormant seed; pull as much as you can, and never let it go to seed!
This stuff is so nasty I don't even put it in the compost.
My garden blog http://amidwestgarden.blogspot.com/
My cooking blog http://ihopeyouarehungry.blogspot.com/