That's from all research papers on Autism and Asperger's. More say they're two distinct disorders compared to those who state they're the same disorder, but only differing in severity. The disparity of opinions isn't too great however (36 to 23).
It kinda sucks for it leaves those with "HFA" balancing on the diagnostic tightrope (Autistic Disorder without a ret*d verbal IQ as an adult), and one can fall to either side depending on who or what diagnoses you.
Fortunately, the countries that lump "HFA" and AS together treat them the same as "LFA" in gaining social services, so whatever label one has, it is effectively moot.