1. CCITT Recommendation Z.100: Specification and Description Language SDL, AP IX - 35;Annexes A-F to Z.100, COM X - R16, R25-29, R42,1988
2. ISO TC97/SC21: LOTOS - A Formal Description Technique Based on the Temporal Ordering of Observational Behaviour;ISO/IS 8807,1988
3. Fundamentals of Algebraic Specification;Ehrig,1985
4. An Introduction to the CCITT SDL;Rockström,1985