Every Knowledge Soup fact explainer should make its evidence easy to find.
What we link to
Our preferred sources include original research, official statistics, government and scientific agencies, museums, universities, archives, standards organizations, and first-party historical records. Source links appear in the article or in a clearly labeled sources section.
How to read our sources
A source supports the specific claim attached to it; it should not be treated as an endorsement of every statement on this website. Scientific understanding can change, and older figures may be revised as better evidence becomes available.
Report a possible error
If you believe a claim, date, quotation, image, or source link is wrong, please include the article URL and the evidence that prompted your concern. Contact us through our official X profile.