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In this chapter, the search engines analysed in the previous chapters are compared in order to study the common, principal characteristics that an academic search tool has to have. From qualitative aspects such as functioning and exporting to quantitative issues such as coverage, material sources and types of materials, this chapter reviews the advantages and shortcomings of each engine. Thus, Google Scholar is the engine with the broadest coverage, but BASE is the device with the most open access items. Based on profiling services, Microsoft Academic Search is outstanding, while Scirus owns the best search interface and WorldWideScience and CiteSeerx operate the best exporting solutions.