The $6\times 6$ grid is $4$-path-pairable

Abstract: Let $G=P_6\Box P_6$ be the $6\times 6$ grid, the Cartesian product of two paths of six vertices. Let $T$ be the set of eight distinct vertices of $G$, called terminals, and assume that $T$ is partitioned into four terminal pairs ${s_i,t_i}$, $1\leq i\leq 4$. We prove that $G$ is $4$-path-pairable, that is, for every $T$ there exist in $G$ pairwise edge disjoint $s_i,t_i$-paths, $1\leq i\leq 4$.