1. I. Broere, M. Dorfling, W. Goddard, J.H. Hattingh, M.A. Henning and E. Ungerer, Augmenting trees to have two disjoint total dominating sets. Bull. Inst. Combin. Appl.42 (2004) 12–18.
2. X.G. Chen, D.X. Ma and L. Sun, On total restrained domination in graphs. Czechoslovak Math. J.55(130) (2005) 165–173.
3. X. G. Chen, W. C. Shiu and H. Y. Chen, Trees with equal total domination and total restrained domination numbers. Discuss. Math. Graph Theory28 (2008) 59–66.
4. X. Chen, J. Liu and J. Meng, Total restrained domination in graphs. Comput. Math. App.62 (2011) 2892–2898
5. E. J. Cockayne, An upper bound for the restrained domination number of a graph. Unpublished Manuscript circa 1999.