Duckduckgo claims to use 400 sources [0], so you’re probably not totally spot on.

Edit: However, that includes their Instant Answers feature, and the numbers are outdated, it’s 1600 sources, most of which are catering to an specific and tiny niche (like angular.js docs, or a dictionary of accounting terms). Main sources are Bing, Yahoo, Wolfram Alpha and their own crawler (according to Wikipedia).

[0] https://help.duckduckgo.com/duckduckgo-help-pages/results/so...