Construction of Gray maps for groups of order 16
  In this paper we consider Type 1 Gray maps and Type 2 Gray maps for groups of order 16. First, we confirm that we can construct Type 1 Gray maps for all groups of order 16, and we actually construct them. Next, we confirm that we can construct Type 2 Gray maps for several groups of order 16, and we construct all such maps. Finally we reveal why the other groups do not admit Gray maps. 
Ko Sakai and Yutaka Sato
cs.IT math.IT