I found this paper which runs through the mathematical constructs of the majority of what GH has to offer and then on top of it applies it to architecture by way of analyzing Gehry's work.
By far the most readable, clear, concise and complete work through of the math concepts that GH uses that I have seen.
It is a 334 page long PDF file with excellent graphics.
Good God, where did my link go?! =O
Oh here it is, sorry for the suspense.
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