Participation in RIMSs may also vary by discipline. Thelwall and Kousha  examined the coverage of Scopus-indexed articles with DOI identifiers in ResearchGate and found that the arts, humanities, and some areas of social sciences were highly underrepresented relative to other disciplines. Mas-Bleda and colleagues , who studied the online presence of highly cited researchers working at European institutions, found that an online presence in a RIMS was higher among researchers in the social sciences, engineering, and health sciences than among those in the life sciences and physical sciences.