Google Scholar searches academic publishers, professional societies, online repositories, universities and other web sites. Be aware that many of the results that Google Scholar returns are not peer-reviewed journal articles. Still, it can be a helpful tool for searching a broad range of sources that go beyond those available in library databases.
ProQuest Dissertations & Theses A&I
Most dissertations in this database are not available in full text, and can be difficult to obtain because they're only held by the library at the university where the dissertation was completed. If you find a dissertation related to your topic, use the References tab (if available) to view the complete references list and identify literature on your topic.