Special thanks to Béla and Gabriella Bollobás, Doug Carlston, and Tomi Pierce for providing me with access to places I could not have seen (Bollobás) or worked in (Carlston/Pierce) otherwise. George Jewsbury and Catherine Durandin and Hugo Durandin DeSousa provided timely assistance. Greg Bear lent me two books; I promise to return them! And for talking to me about gunpowder, and listening equably to the occasional rant about Alchemy, thanks to Marco Kaltofen, P. E., of the Natick Indian Plantation and Needham West Militia Companies.