Universal decimal classification:   Classes 50 -51 -52 -53 

 - London:   British standars instituttion,   1943. 
 - 103 p. 
 - British Standars 1000 .
 - British Standars 1000 .
<br/><br/><label>Subjects--Topical Terms: </label><br/>SISTEMA DE CLASIFICACION<br/>CIENCIA<br/>MATEMATICAS<br/>ASTRONOMIA<br/>FISICA