Danelle, Sorry I don't have the link. The article was given to me by a doctor when my children became sick several years ago. You could probably get it through a hospital library, or on the net somehow. I know there is another article that states degrees of impairment such as mild, moderate, severe, etc. I had this article at one time, too, but can't find it. I think it was written by Blair Grubb but I'm not sure. I have 4 file boxes full of articles. Wish I could be of more help. Lori