SAGE and differential calculus

I've finished a book on SAGE and differential calculus. The idea was to simply take the old book Granville's Elements of Calculus, which is public domain now, and slightly modernize and "SAGE-ify" it. The source code, with the pdf form (and the pdf scan of the original book of Granville) can be found at
http://www.opensourcemath.org/books/granville-calculus/ or
http://sage.math.washington.edu/home/wdj/teaching/.
It is open-source and about 230+ pages printed. Hope it is useful for some people.
It is not quite in it's final form, so if you find typos, of have comments, please feel free to email me.