Concept
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Created by Boundless
The First Crusade
Source
Boundless vets and curates high-quality, openly licensed content from around the Internet. This particular resource used the following sources:
"PeoplesCrusadeMassacre.jpg."
https://en.wikipedia.org/wiki/First_Crusade#/media/File:PeoplesCrusadeMassacre.jpg
Wikipedia
CC BY-SA 3.0.