Highway research record.no,156 classification safety factor terrain,and bearing 

 - Washington,  National Research Council, Highway Research Board,  1963-1973. 
 - 479 no.  25 cm. 
 - <-1973>: Publication - National Research Council .
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<br/><br/><label>ISSN: </label>0073-2206 
<br/><br/><label>Subjects--Topical Terms: </label><br/>NUST / MCE<br/>Roads--Design and construction.<br/>Roads.
<br/><br/><label>Dewey Class. No.: </label>624.151  / NAT