There's no paper. I expect stuttering is like many other things. You need to find the treatment that works for the individual. The individual needs to be willing to work at it. Mental health is a factor. Not everyone will achieve 100% fluency. I think that for a stutterer who has yet to make any progress towards fluency, it does feel like it's permanent. That they will be a stutterer forever. It's a mindset that people spend years believing. It's quite powerful. When a suggestion or idea threatens a belief, most people will hold their belief tighter. I think more stutterers can achieve fluency than do. I'm not suggesting it's easy. I think I was fortunate to have found a program that works for me. I don't think I could have achieved it by reading books on stuttering, youtube, or other self help methods. Maybe those work for some folks. I needed the supervision and guidance of the speech pathologist I worked with.