HELP! I'm being overwhelmed by Creeping Buttercup!?

Question:Last year to get rid of this evil, vile weed (never let it's happy yellow flowers fool you) I had 2 loads of topsoil and heavy black liner put over it. I worked like a damn dog for weeks and thought HA!

I was also trying to rid myself of Lillies of the Valley, another one who won't take "no" for an answer. After all that, and all my planting, mulching and loving--these two party crashers are back with a venegance.

Round up? They laugh at Roundup, it's like Martini's at the club for them. Pulling and digging? Neither one is easily dislodged.

Any tried and true remedies that I'm unaware of? Burning the yard down? Move with no forwarding address?

Please if you've had any success against these vicious bastards help me out! Thanks so much, I'm usually not a violent person, but the gauntlet has been thrown!

Answers:
OMG that was so funny! I still can't stop laughing! I have that "buttercup" thing and it's been doing nothing but getting bigger over the years. I just recently took one of it's "babies" to the front part of my landscape. As for getting rid of it, my girlfriend would kill me. She loves those little yellow flowers. I always wondered why it was so big this year! "Creeping", huh!! Well I can't help u out other then just to keep up the fight... oh try weed-b-gone concentrate....i use it on tree stumps and it kills them completely..."do not dilute it with water" ...just pour it out all over the flowers and the root system and this will surely work!