Jespersen, James. <br/><br/>
From sundials to atomic clocks :   understanding time and frequency 

 - Gaithesburgh :   U.S.Department of Commerce,   1999. 
 - 308 p. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>TIEMPO<br/>RELOJES
<br/><br/><label>Universal Decimal Class. No.: </label>529.78