Triangle $△DEF$ is similar to triangle $△GHI$, such that $D$, $E$, and $F$ correspond to $G$, $H$, and $I$ respectively. The length of each side of triangle $△GHI$ is 4 times the length of its corresponding side in triangle $△DEF$. The measure of side $GH$ is 28. What is the measure of side $DE$?