What are good ab workouts for someone with back problems?

I have minor back problems that i received therapy for in the past, can anyone recommend to me any safe workouts for my abs?

Public Comments

1. I've learned that back problems occur from weak abs and a weak core. start slow with crunchies and add extra reps as the weeks go on.
2. My mother has minor lower back pain. Her doctor recommended seeing a chiropractor and simple ab workout. One I know off the top of my head is sit on the ground, hug your knees to your chest, roll back and up again.