TY  - BOOK
AU  - Howson,Colin
TI  - Logic with trees: an introduction to symbolic logic 
SN  - 0415133424
AV  - BC135 .H51
PY  - 1997///
CY  - London, New York
PB  - Routledge
KW  -  
KW  - Logic, Symbolic and mathematical
ER  -