@INPROCEEDINGS{Antoy01PPDP,
 author = {Sergio Antoy},
 title = {Constructor-based conditional narrowing},
 booktitle = {Proc.\ of the 3rd ACM SIGPLAN international conference on Principles and practice of declarative programming},
 year = {2001},
 isbn = {1-58113-388-X},
 pages = {199--206},
 location = {Florence, Italy},
 doi = {http://doi.acm.org/10.1145/773184.773205},
 publisher = {ACM Press},
 }