Start by searching in several relevant databases once you’ve established your search strategy. Don’t evaluate the results yet.
Remove all duplicate references using the above software.
Evaluate the title of each reference you have found. If it sounds relevant keep it, otherwise discard this reference or mark it as discarded.
Now read the abstracts of the remaining references and determine if you still think they might be relevant for your research. Discard any articles that are clearly irrelevant.
Before ordering the books and articles you have found, evaluate them according to the principles named earlier. Is it a reliable publisher, author, etc. If you can see that there’s a problem with the research already at this stage, there’s no sense including it in your thesis.
Acquire the remaining articles as described in “Obtaining Sources” and determine if they are still relevant for your thesis. When reading the articles, pay close note to the references they cite. This is often the best way to find “grey literature” and data sources such as government reports, databases, etc.
Search for additional literature such as updated versions of government reports that were cited in an older article, relevant sources of data, etc. Evaluate and order relevant items.
This flowchart shows how to select a manageable amount of sources for your thesis in an efficient way and is based upon the flow-chart in the PRISMA-statement.