An operational specification model for process control softwareKull, AnuPreprints 11th IFAC World Congress "Automatic Control in the Service of Mankind" : Tallinn, Estonia, USSR, August 13-17, 1990. Vol. 71990 / p. 269-272 Verification, testing and validation of rule-based expert systemsTepandi, JaakPreprints 11th IFAC World Congress "Automatic Control in the Service of Mankind" : Tallinn, Estonia, USSR, August 13-17, 1990. Vol. 71990 / p. 162-167