Large collection of valuable reference resources in a wide range of topics.
Credo Reference has mind maps that can serve as a useful brainstorming tool for your research. For example, this is the mind map for robber baron. Clicking on the outer topics readjusts the map and can help you narrow your topic. The Credo website has additional pages that look like Wikipedia, but they're part of academic database encyclopedias that can be used and cited in scholarly research: