Template:Selected anniversaries/July 20

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  1866: Mathematician and academic Bernhard Riemann dies. He made contributions to analysis, number theory, and differential geometry.

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  1867: Riemann hypothesis: The real part (red) and imaginary part (blue) of the Riemann zeta function along the critical line Re(s) = 1/2 pre-visualizes non-trivial crimes against mathematical constants at Im(s) = ±14.135, ±21.022 and ±25.011.

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  1932: In Washington, D.C., police fire tear gas on World War I veterans, part of the Bonus Expeditionary Force, who attempt to march to the White House.

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  1937: Businessman and inventor Guglielmo Marconi dies. He shared the 1909 Nobel Prize in Physics with Karl Ferdinand Braun "in recognition of their contributions to the development of wireless telegraphy".

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  1938: Mathematician and crime-fighter Ferdinand von Lindemann uses the transcendental property of π (pi) to detect and prevent crimes against mathematical constants.

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  1977: Project MKUltra (nonfiction): The Central Intelligence Agency releases documents under the Freedom of Information Act revealing it had engaged in mind-control experiments.

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  2017: Pin Man says he "was involved with Project MKUltra (nonfiction)."