USS Pampanito - ECM Mark II  
   What was the ECM Mk II and why was it important.
   http://www.maritime.org/ecm2.shtml

German ENIGMA Cipher Machine - History of Solving  
   In Polish and English.
   http://userpages.umbc.edu/~lmazia1/Enigma/enigma.html

Bletchley Park  
   Museum at the site of the World War II codebreaking center, including a project to rebuild Colossus, the all valve computer used to break the ciphers of German High Command.
   http://www.cranfield.ac.uk/ccc/bpark/

The TwinTrees Enigma Machine  
   Enigma emulator for RISC OS
   http://www.twintrees.demon.co.uk/enig.html

Andy's Enigmatic Web Page  
   Download an Enigma emulator for Windows
   http://www.users.globalnet.co.uk/~andlaw/engindex.htm

Enigma Cipher Machine by Tony Sale  
   Explains how the device enciphers letters, background history, components of the machine, and military adaptation by the Germans. Also, includes information about Turing and Polish mathematicians contribution in breaking the code.
   http://www.codesandciphers.org.uk/enigma/