Schaerf (1998). "Programming in Alma-0, or Imperative and Declarative Programming Reconciled". Krzysztof R. Apt, Andrea Schaerf (1998). "Integrating Constraints into an Imperative Programming Language". Krzysztof R. Apt, Andrea Schaerf (1999). "The Alma Project, or How First-Order Logic Can Help Us in Imperative Programming". Modula programming language family Systems programming languages Procedural programming languages Logic programming languages Multi-paradigm programming languages Programming languages created in the 20th century Constraint programming languages