  It is known to be a hard problem to compute the competition number k(G) of a
graph G in general. Park and Sano [13] gave the exact values of the competition
numbers of Hamming graphs H(n,q) if $1 \leq n \leq 3$ or $1 \leq q \leq 2$. In
this paper, we give an explicit formula of the competition numbers of ternary
Hamming graphs.
