  In 1982, Opsut showed that the competition number of a line graph is at most
two and gave a necessary and sufficient condition for the competition number of
a line graph being one. In this note, we generalize this result to the
competition numbers of generalized line graphs, that is, we show that the
competition number of a generalized line graph is at most two, and give
necessary conditions and sufficient conditions for the competition number of a
generalized line graph being one.
