“…Moreover, document content from citation networks can be the basis for entity networks representing relationships for knowledge units such as drugs (Ding et al, 2013). As it is the case for citation (Kim and Barnett, 2008) and collaboration networks (Ding, 2011), keyword-based bibliometric analyses and social network analysis were also combined in multiple studies (Bodlaj and Batagelj, 2014; Hu et al, 2013; Su and Lee, 2010), for example, to create complex co-keyword networks and keywords co-occurrence networks (Cheng et al, 2018; Kastrin et al, 2014; Li et al, 2016). Yet recently, subject headings are still used separately for mapping science (Shu et al, 2017), to detect journal similarity (Yan and Chien, 2021) or in combination with co-citation and other metrics (Cabeza Ramrez et al, 2019).…”