http://espresso-for-geeks.kalaf.net/
http://espresso-for-geeks.kalaf.net/features/
http://espresso-for-geeks.kalaf.net/features/pid-water-temperature-control/
http://tomblog.firstsolo.net/index.php/hobbies/pimping-my-coffee-machine/
http://tomblog.firstsolo.net/index.php/solved-temperature-control/