Distance-2 Edge Coloring is NP-Complete
  We prove that it is NP-complete to determine whether there exists a distance-2 edge coloring (strong edge coloring) with 5 colors of a bipartite 2-inductive graph with girth 6 and maximum degree 3. 
Jeff Erickson (1), Shripad Thite (1), David P. Bunde (1) ((1)   Department of Computer Science, University of Illinois at Ur...