“…Such a method divides the density matrix into fragments that are treated by conventional quantum chemistry techniques to ultimately obtain the properties of the whole system. Later, Merz and coworkers developed a semiempirical version of divide-and-conquer (Dixon & Merz, 1996, 1997; Ermolaeva, van der Vaart, & Merz, 1999), Exner and Mezey proposed the adjustable density-matrix assembler approach (Exner & Mezey, 2002, 2003, 2004), Zhang and coworkers developed the molecular fractionation with conjugated caps approach (Gao, Zhang, Zhang, & Zhang, 2004; Kurisu, Zhang, Smith, & Cramer, 2003; Mei, Zhang, & Zhang, 2005; Zhang, Xiang, & Zhang, 2003; Zhang & Zhang, 2003), Gadre and coworkers developed the molecular tailoring approach (Babu & Gadre, 2003; Babu, Ganesh, Gadre, & Ghermani, 2004; Gadre, Shirsat, & Limaye, 1994), Kitaura and coworkers proposed the fragment molecular-orbital FMO method (Fedorov & Kitaura, 2004a, 2004b; Kitaura, Ikeo, Asada, Nakano, & Uebayasi, 1999; Kitaura, Sugiki, Nakano, Komeiji, & Uebayasi, 2001), Li and coworkers proposed the localized molecular-orbital assembler approach (Li & Li, 2005; Li, Li, & Fang, 2005), Mayhall and Raghavachari proposed the multilayer molecules-in-molecules method that is similar in spirit to the ONIOM approach (Mayhall & Raghavachari, 2011) (vide infra), while Collins and Bettens introduced the combined and systematic fragmentation approach (Collins, Cvitkovic, & Bettens, 2014). …”