1. ZeTa system (August 1997),
http://uebb.cs.tu-berlin.de/zeta/
2. HOL-TestGen (January 2005),
http://www.brucker.ch/projects/hol-testgen/
3. ProofPower (January 2005),
http://www.lemma-one.com/ProofPower/index/
4. Isabelle/HOL-OCL (March 2006),
http://www.brucker.ch/projects/hol-ocl/
5. Isabelle/HOL-Z (January 2007),
http://www.brucker.ch/projects/hol-z/