“…An avalanche of studies exploring new data sources took place at the beginning of the decade, with the launch of Web of Science's Book Citation Index (Leydesdorff and Felt, 2012;Gorraiz, Purnell and Glänzel, 2013;Torres-Salinas, Robinson-Garcia, et al, 2014), the inclusion of books in Scopus (Kousha, Thelwall and Rezaie, 2011) and the increase in research focused on Google Scholar (Kousha, Thelwall and Rezaie, 2011) and Google Books (Abdullah and Thelwall, 2014;Kousha and Thelwall, 2015a). They have also brought to light some of the characteristics and peculiarities (Torres-Salinas et al, 2012, 2013Torres-Salinas, Robinson-García, et al, 2014;Chi, 2016;Glänzel, Thijs and Chi, 2016), which cannot be discerned on the basis of micro-analytic case studies or small samples of data.…”