This is a nightmare and often a life sentence. All you can really do is keep digging it out the minute you see it so it never has a chance to grow. The roots go very deep indeed so you can't dig them all out, but constant vigilance will eventually starve it to death. Be especially careful to remove the different stalks with little knobs on the top that appear in spring, as these are the spore bearing heads that will spread by "seed" dispersal as well as by root runners.