These online encyclopedias are a good place to delve into your topic and get new ideas. They often also include references to research publications. You shouldn't cite encyclopedias in your academic papers, though! They're best used at the start of the research process.
Confused about what constitutes empirical research? Can't tell quantitative from qualitative? Or have you run into a new method, and you want more information? These books should provide the overview you need. As with other encyclopedias, don't cite these as sources in your research papers.