- Jimmy Carter (Wikipedia)
James Earl Carter Jr. (born October 1, 1924) is an American politician and humanitarian who served as the 39th president of the United States from 1977 to 1981. A member of the Democratic Party, Carter was the 76th governor of Georgia from 1971 to 1975, and a Georgia state senator from 1963 to 1967. At age 99, he is both the oldest living former U.S. president and the longest-lived president in U.S. history.
- Klein bottle (Wikipedia)
In mathematics, the Klein bottle (/ˈklaɪn/) is an example of a non-orientable surface; that is, informally, a one-sided surface which, if traveled upon, could be followed back to the point of origin while flipping the traveler upside down. More formally, the Klein bottle is a two-dimensional manifold on which one cannot define a normal vector at each point that varies continuously over the whole manifold. Other related non-orientable surfaces include the Möbius strip and the real projective plane. While a Möbius strip is a surface with a boundary, a Klein bottle has no boundary. For comparison, a sphere is an orientable surface with no boundary.