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I’m still not understanding how you know if it’s is copywrited or not. If it was taken or created in the USA it is copywrited unless explicitly stated that it’s not by the artist

Inside Google immages there is a tool that allows you to search images without copyright. I made you a screenshot. It is written in Italian (because I am Italian), however you can classify images according to your preferences (with copyright, without copyright)
Schermata_2018-05-23-21-45-14-501.jpeg
If you have any other question, tell me

A very useful tool, thanks!