This image was acquired from
wikimedia. It was marked as Public Domain or CC0 and is free to use. To verify, go to the source and check the information there.
Keywords from Image Description:
Figureknotmathsquare.svg Figureeight knot of mathematical knot theory in simple square depiction For different curvy visual depiction see File Figureknotmathematicalknottheory svg For an alternative topologicallyequivalent representation of the knot see File Figureknotmathsquarealternate svg Selfmade graphic generated from the following