Need some statistics? Use either a Library Database:
Or a Government Data Source:
Look for a National Organization or Governmental Organization to help write your Rationale. The easiest way to do this is through at Advacned Google Search:
You can put your topic or interest the in first search box, then look for the Narrow option that allows you to search for a specific Site or Domain. Try .org, .gov, or .edu to target your search:
Then you'll get more targeted results that you can use: