TY  - BOOK
AU  - Hughes,G E.
AU  - Cresswell,M J  .
TI  - A new introduction to modal logic / 
SN  - 0415126002
U1  - 160 
PY  - 2005///
CY  - London : 
PB  - Routledge , 
KW  - LOGIC
N1  - Includes bibliography & index
ER  -