@inproceedings{G1991,
author = {J.W. Grzymala-Busse},
title = {On the Unknown Attribute Values In Learning From Examples},
booktitle = {6th International Symposium on Methodologies For Intelligent Systems({ISMIS\\91})},
city = {Charlotte},
country = {USA},
pages = {368--377},
year = {1991}
}