  We define an operation on finite graphs, called co-contraction. By showing
that co-contraction of a graph induces an injective map between right-angled
Artin groups, we exhibit a family of graphs, without any induced cycle of
length at least 5, such that the right-angled Artin groups on those graphs
contain hyperbolic surface groups. This gives the negative answer to a question
raised by Gordon, Long and Reid.
