Unterberger, Robert R. <br/><br/>
Sonar probing as a mining and tunneling tool :  progress report September 1, 1977 - June 1, 1978 / 
submitted to National Science Foundation ; submitted by Robert R. Unterberger. 
 - vii, 65, [36] leaves :  illustrations ;  28 cm. 
<br/><br/> Photocopy of NTIS publication PB-289810.  "This material is based upon work supported by the National Science Foundation under Grant No. APR 76-21764."  "Report Date: June 1, 1978." 
<br/><br/>Includes bibliographical references (leaf 4-29). 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Sonar.<br/>Rock salt.<br/>Tunneling--Equipment and supplies--Testing.<br/>Sonar.<br/>Rock salt.