@INPROCEEDINGS { Rsds2550,
author = {Polkowski, Lech T. and Semeniuk-Polkowska, Maria}, 
title = {Conjugate Information Systems: Learning Cognitive Concepts in Rough Set Theory}, 
booktitle = {Rough Sets, Fuzzy Sets, Data Mining, and Granular Computing}, 
series =  = {Lecture Notes in Artificial Intelligence}, 
volume = 2639, 
pages = {255--258}, 
publisher = {Springer-Verlag}, 
address = {Heidelberg - Berlin, Germany}, 
month = {May}, 
year = 2003, 
editor = {Wang, Guoying and Liu, Quing and Yao, Yiyu and Skowron, Andrzej}, 
issn = {0302-9743}, 
isbn = {3-540-14040-9}, 
abstract = {The problem of concept learning [1] via rough sets has been recently discussed in literature e.g. cf. [6], [3], [7]. To formally study this problem, we introduce a notion of a conjugate information system cf. [3].}, 
keywords = {rough sets, information systems, conjugate information systems, learning of cognitive concepts, }, 
}