THE ELECTRONIC JOURNAL OF COMBINATORICS 4 (1997), DS #5. |

Footnotes

^{1} By *C*(*n*,*k*) we denote the binomial
coefficient *n*!/(*k*!(*n*-*k*)!).

^{2} Two figures in the plane are *congruent* if one
can be transformed into the other by rotations and translations in
the plane.

^{3} A graph is *three-connected* if the removal of
any two vertices (and the adjacent edges) leaves a connected graph.

^{4} The *prism* of a graph *G* is formed by taking two copies
of *G* and adding a perfect matching whose edges join
corresponding copies of vertices.

^{5} A *planar graph* is one that can be embedded in the plane
without crossing edges. A *plane* graph is a planar graph that has
been embedded in the plane.

^{6} The *square* of a graph G, denoted G^{2}, is the graph
obtained from G by adding edges between vertices if they are at distance 2
in G.
All of the original edges of G are present in G^{2}.

^{7} A *link* is a finite collection of knots.
A *Brunnian link* is a link which is non-trivial,
yet every proper sub-collection is trivial.
A trivial link is one that can be projected to a collection of
circles in the plane.

THE ELECTRONIC JOURNAL OF COMBINATORICS 4 (1997), DS #5. |