Harder, Leslie F. <br/><br/>
Determination of penetration resistance for coarse-grained -soils using the becker hammer drill / by Leslie F. Harder a-nd H. Bolton Seed 

 - Berkeley, Calif. : e Engineering Research Center 
 - 134 p. 
 - Report ; No.UCB / EERC 86-06 .
<br/><br/> "A report on research sponsored by the National Science Fou-ndation""May 1986"