  The $g$-girth-thickness $\theta(g,G)$ of a graph $G$ is the minimum number of
planar subgraphs of girth at least $g$ whose union is $G$. In this note, we
give the $4$-girth-thickness $\theta(4,L(K_n))$ of the line graph of the
complete graph $L(K_n)$ when $n$ is even. We also give the minimum number of
subgraphs of $L(K_n)$, which are of girth at least $4$ and embeddable on the
projective plane, whose union is $L(K_n)$.
