@article{DBLP:journals/cacm/Ledgard72,
author = {Henry F. Ledgard},
title = {A Model for Type Checking - with an Application to ALGOL
60},
journal = {Commun. ACM},
volume = {15},
number = {11},
year = {1972},
pages = {956-966},
ee = {http://doi.acm.org/10.1145/355606.361876},
bibsource = {DBLP, http://dblp.uni-trier.de}
}