Citation mining: when you find a relevant item you can use it to find more resources.
1. You can build upon past research by review the item's bibliography for additional leads.
Look at the citations from the bibliography of a great source and then go track those sources down. This leads back in time to related works.
2. You can see where the conversation has gone or is going by determining who has cited this article.
Once you have found a relevant article on GoogleScholar or in ScienceDirect, look for the "cited by" option and read those.
Find data at the national and international levels. Both original datasets as well as commercially-packaged data.
Zotero is a tool that helps you to collect, manage, and cite your references