My manuscript "Calculus of extensive quantities" is available at arXiv, http://arxiv.org/abs/1105.3405 This is a companion to the preprint "Monads and extensive quantities" (announced on the list on March 31), but it is more elementary (using partly a "synthetic" exposition style). The phrase "calculus" in the title of the present preprint refers in particular to one-variable differential calculus. Anders Kock [For admin and other information see: http://www.mta.ca/~cat-dist/ ]