@article{DMGT_2005_25_3_a7,
     author = {Chellali, Mustapha and Khelladi, Abdelkader and Maffray, Fr\'ed\'eric},
     title = {Exact double domination in graphs},
     journal = {Discussiones Mathematicae. Graph Theory},
     pages = {291--302},
     publisher = {mathdoc},
     volume = {25},
     number = {3},
     year = {2005},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/DMGT_2005_25_3_a7/}
}