[1] HENNING M. A.-OELLERMANN O. R.-SWART H. C.: Bounds on distance domination parameters. J. Combin. Inform. System Sci. 16 (1991), 11-18. MR 1176392 | Zbl 0766.05040
[2] LEMANSKA M.: Lower bound on the domination number of a tree. Discuss. Math. Graph Theory 24 (2004), 165-169. MR 2120560 | Zbl 1063.05035