Template:Selected anniversaries/July 20
1866: Mathematician and academic Bernhard Riemann dies. He made contributions to analysis, number theory, and differential geometry.
1889: Mark Twain alleges that Baron Zersetzung is "trafficking in Clandestiphrine and Extract of Radium, to the detriment of clear and rational thought, relentless seeking to corrupt, usurp, and digest what remains of the Republic."
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".
1938: Mathematician and crime-fighter Ferdinand von Lindemann uses the transcendental property of π (pi) to detect and prevent crimes against mathematical constants.
1977: Project MKUltra (nonfiction): The Central Intelligence Agency releases documents under the Freedom of Information Act revealing it had engaged in mind-control experiments.
2017: Pin Man says he "was involved with Project MKUltra (nonfiction)."