Google Scholar is a freely accessible web search engine. Its index includes most peer-reviewed online academic journals and books, conference papers, theses and dissertations, preprints, abstracts, technical reports, and other scholarly literature, including court opinions and patents ResearcherID is an identifying system for scientific authors (introduced in January 2008 by Thomson Reuters Corporation). This system is fully integrated with "Web of Science", which is an online scientific citation indexing platform. Web of Science Citation Indexes allow to search information in such disciplines as agriculture, biological sciences, engineering, medical and life sciences, physical and chemical sciences, anthropology, law, library sciences, architecture, dance, music, film, and theater SciVerse Scopus is the largest abstracts and citations database of Elsevier’s SciVerse, that integrates the familiar–trusted content from SciVerse Scopus, peer-reviewed literature, SciVerse ScienceDirect full-text articles and the Web