@article{10_37236_689,
     author = {Xue-gang Chen and Wai Chee Shiu},
     title = {A new upper bound on the global defensive alliance number in trees},
     journal = {The electronic journal of combinatorics},
     year = {2011},
     volume = {18},
     number = {1},
     doi = {10.37236/689},
     zbl = {1230.05224},
     url = {http://geodesic.mathdoc.fr/articles/10.37236/689/}
}