@article{KJM_2015_39_2_a1,
     author = {J. Amjadi},
     title = {An upper bound on the double domination number of trees},
     journal = {Kragujevac Journal of Mathematics},
     pages = {133 },
     publisher = {mathdoc},
     volume = {39},
     number = {2},
     year = {2015},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/KJM_2015_39_2_a1/}
}