Harary, Frank, <br/><br/>
Structural models :  an introduction to the theory of directed graphs / 
by Frank Harary, Robert Z. Norman, Dorwin Cartwright 
 - ix, 415 páginas 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Ciencias sociales--Modelos matemáticos
<br/><br/><label>LC Class. No.: </label>H61  / H3