http://www.connel.net/freeware/airduct.shtml

http://www.howstuffworks.com/

http://www.mcnallyinstitute.com/index.html

http://www.automatedbuildings.com/

http://www.refrigerants.com/index.htm

http://grunerbrass.com/refriger.htm

http://www.utahstangs.com/tech/turbo/compformula.htm

ab absurdo