TY  - BOOK
AU  - Vacca,John R.
TI  - The world's 20 greatest unsolved problems / 
SN  - 0131426435
U1  - 500 
PY  - 2005///
CY  - Upper Saddle River, NJ
PB  - Prentice Hall, 
KW  - Natural Sciences
KW  - Natural sciences
ER  -