Twito, Roger H. <br/><br/>
Determining average distance / 
Roger H. Twito and Charles N. Mann 
 - Washington, D.C. :  U.S. Government Printing Office,  1979 
 - 29 p. ;  26 cm. 
<br/><br/> General technical report no. PNW-79  Forest service  Pacific North West forest and range experiment station 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Air traffic control--United States<br/>Aids to air navigation--United States<br/>Air-pilot guides--United States
<br/><br/><label>Dewey Class. No.: </label>629.132520973