Constraint Theory, Part I: Fundamentals. - George J. Friedman; Cornelius T. Leondes (IEEE Trans. Syst. Sci. Cybern., 1969)

Constraint Theory, Part II: Model Graphs and Regular Relations. - George J. Friedman; Cornelius T. Leondes (IEEE Trans. Syst. Sci. Cybern., 1969)

Constraint Theory, Part III: Inequality and Discrete Relations. - George J. Friedman; Cornelius T. Leondes (IEEE Trans. Syst. Sci. Cybern., 1969)