National seismic system science plan, / 
by Thomas H. Heaton...[et al.] 
 - Washington :  U.S. Dept. of the Interior, Geological Survey,  1989 
 - iv,42 p. :  ill. ;  26 cm. 
 - Annual 
 - Geological Survey circular ;  1031 .
<br/><br/><label>Subjects--Topical Terms: </label><br/>Earthquake--Seismology
<br/><br/><label>Dewey Class. No.: </label>551.22