PQS: "I dont know" Is an Important Qualitative Statement. - Toal, A. F. (1992)

Spatio-temporal Reasoning within a Traffic Surveillance System. - Toal, A. F.; Buxton, Hilary (1992)

P.Q.S.: building and using an advanced qualitative simulator utilizing explicit nondeterminism. - Toal, A. F. (1991)