@article{DBLP:journals/actaC/Nestra02,
author = {H{\"a}rmel Nestra},
title = {Framework for Studying Substitution},
journal = {Acta Cybern.},
volume = {15},
number = {4},
year = {2002},
pages = {633-652},
ee = {http://www.inf.u-szeged.hu/kutatas/actacybernetica/vol15n4/cikk10.xml},
bibsource = {DBLP, http://dblp.uni-trier.de}
}