How many books are there in Simplified?

I have an interesting question for you.
I would like to know ALL the books that were published for simplified, because as I search for them on amazon/ebay/etc..., there are so many!
Here's what I currently have in my possession:
The 'book'--Gregg Shorthand Simplified, Second Edition
The 'dictionary'
The 'phrase book'
The "Speed building"
there seem to be so many more, and I don't know if just the covers of the book changed, or they are completely different books.  Is the 'functional method' book any different than the Second Edition simplified text book?  They look different in the picture;  different cover, different title.
Then there is the shorthand for colleges.  What's the difference between that and the others?
You can see that one who is not yet entirely familiar with all of this can be a little confused when searching for books!!
Thanks for your help, and I think it may clear up some questions others may have too!

(by bob1106 for everyone)