Scholarly sources, which are normally published in journals, as book chapters, or in conference proceedings, usually cover specific topics at a fairly deep level. In Industrial and Systems Engineering, scholarly sources may include journal articles and papers in conference proceedings.
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A scholarly database organizes the best quality, most relevant information for a field or discipline in one place so it can be searched. Because there is so much scholarly research and so many different fields, databases specialize in which kinds of information or tools they provide.
Scholarly databases take into account the important publications and research methods of a field or discipline. The database helps you make choices about which articles you want to see - by subject, dates of publication, overall topic, and more. Google and Google Scholar, while vast, do no quality control on the content they provide or give you good tools to narrow your focus.