Hill, L.A. <br/><br/>
Advanced steps to understanding 
/ L. A. Hill 
. - New York  : Oxford university press, 1985
. - 78 p.  : ill.  ; 22 cm. 
<br/><br/><label>ISBN: </label>0195818555 
<br/><br/><label>Source: </label> Achat 
<br/><br/><label>Universal Decimal Class. No.: </label>802.08