“…Many practical applications of the MLSTP/MCDSP (equivalent to the RLP) are discussed in Lucena et al (2010) and Gendron et al (2014) . Since the problem is N P -hard, researchers have studied exact algorithms ( Chen et al, 2010;Fan & Watson, 2012;Fujie, 2003;Gendron et al, 2014;Lucena et al, 2010;Simonetti, Salles da Cunha, & Lucena, 2011 ), heuristics ( Chen et al, 2010;Duarte, Martí, Resende, & Silva, 2014;Lucena et al, 2010;Sen et al, 2008;Yue, Li, Wei, & Lin, 2014 ), and approximation algorithms ( Flammini, Marchetti-Spaccamela, Monaco, Moscardelli, & Zaks, 2011;Guha & Khuller, 1998 ) for solving these problems.…”