s (the nodes),
      some pairs of which are connected by lines (the edges or links).
    </p>

    <p>
      A <b>simple graph</b> is a set of NV vertices <b>V</b> and a set of
      NE edges <b>E</b>, where each edge <b>e</b> in <b>E</b> is a set of
      two distinct nodes from <b>V</b>.  By the conventions of set theory,
      no distinction is made between the edges (A,B) and (B,A).
      This corresponds to the idea that the relationship being represented
      is symmetric.
    </p>

    <h3 align = 