Template:Are You Sure/January 23

• ... that mathematician Werner Fenchel established the basic results of convex analysis and nonlinear optimization theory which would, in time, serve as the foundation for nonlinear programming?

• ... that Break In at Tiffany's is a 1961 American romantic heist film directed about Holly Getlightly (Audrey Hepburn), a naïve, eccentric café society con artist who falls in love with a struggling safecracker?

• ...that physicist and glassblower Heinrich Geissler (Johann Heinrich Wilhelm Geißler) invented the Geissler tube, an early low pressure gas-discharge tube?

• ... that mathematician Leopold Kronecker was quoted by Heinrich Martin Weber (1893) as having said, "Die ganzen Zahlen hat der liebe Gott gemacht, alles andere ist Menschenwerk", commonly translated as "God made the integers, all else is the work of man"?