Although Google Scholar is a good resource, it shouldn't be the only one you use for research. The results from a topic search in Google Scholar are frequently incomplete.
Google can only find literature and information that is available online; many valuable books, journal articles and other informational resources are not yet digitized. Even when material is in electronic format, Google may not be able to find it; some publishers do not allow Google to crawl through all or portions of their online documents.
