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A History of Mathematical Notations, Florian Cajori

Enlightening Symbols, Joseph Mazur

https://academic.oup.com/philmat/article/14/3/287/1462575

https://link.springer.com/book/10.1007/978-3-642-61779-9

https://link.springer.com/book/10.1007/978-3-642-51599-6

https://www.jstor.org/stable/27963851

https://www.sciencedirect.com/science/article/pii/S031508600600022X

https://jontalle.web.engr.illinois.edu/uploads/298/HistoryMath-Burton.85.pdf

http://math.fau.edu/yiu/PSRM2015/yiu/New%20Folder%20(4)/Downloaded%20Papers/New%20Folder/0-19-852495-1.pdf

https://www.jstor.org/stable/2299605

https://www.jstor.org/stable/27963851

https://www.jstor.org/stable/2972623

https://jontallen.ece.illinois.edu/uploads/537.F18/Papers/MathematicsandItsHistory-johnStillwell.pdf

https://bigthink.com/hard-science/quadratic-formula-history/

https://www.youtube.com/watch?v=r6heVXg73mM

https://theconversation.com/x-marks-the-unknown-in-algebra-but-xs-origins-are-a-math-mystery-210440

https://scholarship.claremont.edu/cgi/viewcontent.cgi

https://ia802209.us.archive.org/9/items/taming-the-unknown-a-history-of-algebra-from-antiquity-to-the-early-twentieth-ce/Taming%20the%20Unknown%20A%20History%20of%20Algebra%20from%20Antiquity%20to%20the%20Early%20Twentieth%20Century%20by%20Victor%20J.%20Katz,%20Karen%20Hunger%20Parshall%20(z-lib.org).pdf

https://www.ams.org/journals/bull/2015-52-04/S0273-0979-2015-01491-6/S0273-0979-2015-01491-6.pdf

https://books.google.com/books?id=I-jwDQAAQBAJ&pg=PA73&lpg=PA73

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https://phys.org/news/2015-06-mathematics-reveals-nature-cosmos.html