“…These journals, the scholars concluded, "should be considered valuable or "core" across the various fields of chemistry". 29 In agreement with findings reported 10 years before by Kousha and Thelwall for which in chemistry, 88.5% of the citations retrieved by Google Scholar were from journal papers, 31 books and book chapters were cited only in 2.4% of the sampled articles, similar to conference proceedings (2.3%), and Web sites and other sources such as brief communications, dissertations, letters to the editor, notes, patents, personal communications, short surveys, and software or software manuals (2.5%). For comparison, in 2008 in physics, e-prints/ preprints accounted for 47.7% of unique citations, and in computer science, conference/workshop papers, 43.2%, were the major sources of citations.…”