Bounds for signed double Roman k-domination in trees Hong Yang, Pu Wu, Sakineh Nazari-Moghaddam, Seyed Mahmoud Sheikholeslami, Xiaosong Zhang, Zehui Shao and Yuan Yan Tang RAIRO-Oper. Res., 53 2 (2019) 627-643 Published online: 05 June 2019 DOI: 10.1051/ro/2018043