TY  - BOOK
AU  - Chellas,B.F.
TI  - Modal logic: an introduction 
SN  - 0521224764
AV  - DUCE BC199.M6C47 
PY  - 1980///
CY  - Cambridge
PB  - Cambridge University Press
KW  - Modality (Logic)
N1  - Includes bibliographical references and indexes
UR  - http://www.loc.gov/catdir/description/cam022/76047197.html
UR  - http://www.loc.gov/catdir/toc/cam028/76047197.html
ER  -