[2] Beyer, T., Proskurowski, A., Hedetniemi, S., Mitchell, S.: 
Independent domination in trees. Proc. Conf. on Combinatorics, Graph Theory and Computing Baton Rouge, 1977, Congressus Numerantium, Utilitas Math., Winnipeg (1977), 321-328. 
MR 0485473 | 
Zbl 0417.05020