Template:Are You Sure/May 20

• ... that logician and mathematician Ernst Zermelo (1871–1953) made pioneering contributions to set theory, notably the Zermelo–Fraenkel axiomatic set theory, as well as his proof of the well-ordering theorem; and that Zermelo's work had major implications for the foundations of mathematics?

• ... that the Flying bison (Bison pterobonasus) is a large, even-toed ungulate in the genus Bison within the subfamily Bovinae, distinguished from other Bovinae by two pairs of strong, transparent wings, and that the wings are used mainly for short bursts of flight, such as jumping across canyons, or engaging in courtship displays?