Cirstea, H. and Kirchner, C. "Combining Higher-Order and first-Order Computation Using - Calculus: Towards a semantics of ELAN" pp95-121

Gabbay, D.M. (1999) Gabbay, D.M. and M. de Rijke editors. Frontiers of Combining Systems 2 Research Studies Press/Wiley, 1999.  

Languages mentioned Elan {1998} Constraint logic program