Apt, K. R., Brunekreef, J. J., Partington, V., & Schaerf, A. (1998). Alma-0 : An imperative language that supports declarative programming. ACM Transactions on Programming Languages and Systems, 20(5), 1014-1066.
Apt, K. R., Brunekreef, J. J., Partington, V., & Schaerf, A. (1997). Alma-0: An imperative language that supports declarative programming. (Technical Report; No. PNA-R9713). CWI.
Partington, V. (1997). Implementation of an Imperative Programming Language with Backtracking. (Technical Report; No. P9712). onbekend (FdL).