A lot of online advice on developing the abs starts by correcting the misperception that the abs are separate muscles, instead, they are a single wall.
Now, it's not clear what should I conclude from it. My problem is that my upper abdomen is shaping up pretty nice and flat as I work on it, but the lower part still has a little bulge and its pretty stubborn. Some people advise that since its one wall, you can't target a particular part of it and you have to continue doing overall ab exercises to reduce it. Others say that you can tone the lower part specifically by increasing the number and intensity of lower ab workouts.
So, I would like some advice on which side to believe, either from personal experiences or any studies that might have been done, etc.