The best search terms will be the main concepts in your research topic. Take the time to choose them carefully, and your searches will be more successful.
For example:
Research question: How does globalization affect women in developing countries?
Search terms: globalization, women, developing countries
Depending on what database you're using, you may find that the terms women and globalization are sufficient without the phrase developing countries. This is especially likely when searching for a book. There may be a book about women and globalization that has a chapter on developing countries, but the whole book is not on that particular aspect.
You should have at least two concepts for your research topic, only one will be too broad, making it difficult to research and to write about.
When searching in an article database, the more specific search terms are usually more successful, and you would probably use all three concepts.
Below is a list of recommended Databases for WSGR
