TY  - BOOK
AU  - Jespersen, James.
AU  - Fitz-Randolph, Jane.
TI  - From sundials to atomic clocks : : understanding time and frequency
PY  - 1999///
CY  - Gaithesburgh : 
PB  - U.S.Department of Commerce, 
KW  - TIEMPO
KW  - RELOJES
ER  -