TY  - BOOK
TI  - Physical forces
T2  - (Understanding Science & Nature)
SN  - 0-8094-9675-5
U1  - Ref. 530 P578 1992 
PY  - 1992///
CY  - Alexandria, Virginia
PB  - Time-Life
KW  - Physics
N1  - Includes glossary and index
ER  -