TY - JOUR AU - Mojdeh, Doost Ali AU - Samadi, Babak AU - Yero, Ismael G. TI - Global defensive $k$-alliances in directed graphs: combinatorial and computational issues JO - RAIRO - Operations Research - Recherche Opérationnelle PY - 2020 SP - 1027 EP - 1040 VL - 54 IS - 4 PB - EDP-Sciences UR - http://www.numdam.org/articles/10.1051/ro/2019049/ DO - 10.1051/ro/2019049 LA - en ID - RO_2020__54_4_1027_0 ER -