Edwin Hubble publishes his discovery that the speed at which galaxies recede positively correlates with their distance, which becomes known as Hubble's law, the basis for understanding that the universe is expanding.
Clinical application of cardiac catheterization begins with German Werner Forssmann who inserts a catheter into the vein of his own forearm, guides it fluoroscopically into his right atrium, and takes an X-ray picture of it.
British surgeon Victor Negus publishes The Mechanism of the Larynx.
^Pompeiu, Dimitrie (1929). "Sur certains systèmes d'équations linéaires et sur une propriété intégrale des fonctions de plusieurs variables". Comptes Rendus de l'Académie des Sciences, Série I. 188. Paris: 1138–9.
^Miller, Rupert G. (1966). Simultaneous Statistical Inference. New York: Springer-Verlag. p. 1. ISBN978-1-4613-8124-2.
^Bernce, Arvid (1981). Efter 1809 en Krönika i ord och bild om Finlandssvenskarna (in Swedish). Helsingfors: Bernces förlag. p. 2003. ISBN978-9-15000-408-3.