The smallest possible <a href="https://en.wikipedia.org/wiki/Zero-symmetric_graph" class="extiw" title="en:Zero-symmetric graph">zero-symmetric graph</a> (a cubic graph whose vertices are symmetric but whose edges fall into three different symmetry classes). Redrawn (in a different style) from Fig. 1.1 of Coxeter, Harold Scott MacDonald; Frucht, Roberto; Powers, David L. (1981), <i>Zero-symmetric graphs</i>, Academic Press, Inc. [Harcourt Brace Jovanovich, Publishers], New York-London, <a href="//commons.wikimedia.org/wiki/Special:BookSources/0-12-194580-4" title="Special:BookSources/0-12-194580-4">ISBN 0-12-194580-4</a>, MR 658666, p. 5.
<a href="//commons.wikimedia.org/wiki/User:David_Eppstein" class="mw-redirect" title="User:David Eppstein">David Eppstein</a>
<span class="int-own-work" lang="en">Own work</span>