Yes. I found that a while ago. They reference a lot of studies and research, but unfortunately only quote small snippets without context in support of their particular take on the world. They also tend to concentrate on studies of children whom are learning to spell, rather than a broad range of age groups or other categorisations, which I am more interested in.

I would dearly like to read many of the original studies that they quote from, but I've had difficulty trying to track them down on the web. I'll probably end up going to the British Library to obtain copies if my interest continues to that level, but hoped that some of the linguist monks might know of better on-line sources than I have found so far.