TY  - BOOK
AU  - "Winter, James De"
TI  - How to catapult a castle: machines that brought down the battlements
T2  - Fact finders Extreme
SN  - 9781429631181
U1  - 000 
PY  - 2008///
CY  - Minnesota
PB  - Capstone Press
N2  - "Presents the science behind building and defending castles including the use of simple machines, such as pulleys and levers"--Provided by publisher
ER  -