If you want great abs, then performing endless sets of ab specific exercises are ab-solutely (pun very much intended) useless.
5 Best Calisthenics Abs Exercises To Get Six Packs At Will
5-Move Abs and Butt Workout
How To Do Crunches Properly For Strong Abs, From A Trainer
7 Abs Exercises You're Probably Doing Wrong—And How To Fix Them
10 Best Lower Ab Exercises for a Strong, Supported Core
Oblique Workouts - Best Exercises for Muscle and Strength
How long will a six pack abs last if you stop working out? - Quora
Stop Doing Crunches - Here's how to get great ABS - Body Solutions
Stop Doing Crunches - Here's how to get great ABS - Body Solutions