“…Various types of relations among publications can be used to establish research topics, such as citation‐based, text‐based, and hybrid approaches. In the case of text‐based approaches, some studies have established clusters based on the co‐occurrence of terms (e.g., Furukawa, Mori, Arino, Hayashi, & Shirakawa, ; Lee, ; see also Rotolo et al, , p. 1834). In the case of citation‐based approaches, different citation relations, for instance direct citation relations (e.g., Kajikawa & Takeda, ; Kajikawa, Yoshikawa, Takeda, & Matsushima, ; Shibata, Kajikawa, Takeda, & Matsushima, ; Shibata, Kajikawa, Takeda, Sakata, & Matsushima, ), bibliographic coupling relations (e.g.…”