Rugg, Donald D. <br/><br/>
The demand for abstract transport modes :  a choice theoretic formulation / 
Donald D. Rugg 
 - California :  Rand Corporation,  1972 
 - 23 pages ;  28 cm. 
 - The Rand paper series ;  p. 4911 .
 - Rand paper series ;  p. 4911 .
<br/><br/>Includes bibliographical references.