of them form a convex quadrilateral. After allowing George, Paul Erdős, and the other students to scratch their heads for some time, Esther explained her proof. Subsequently, George and Paul wrote a paper (1935) that generalises this result; it is regarded as one of the foundational works in the field of combinatorial geometry. Erdős dubbed the original problem the "Happy Ending" problem because it resulted in George and Esther's marriage in 1937. George and Esther died within an hour of each other on 28 August 2005 in Adelaide, South Australia. See also Powerful number Szekeres snark Generalized continued fraction Kruskal–Szekeres coordinates Szekeres–Wilf number Schröder's equation Erdős–Szekeres theorem Notes References Giles, J. R., Wallis, J. S., "George Szekeres. With affection and respect", Journal of the Australian Mathematical Society, Series A, Vol 21 (1976), No 4, pp. 385–392. Cowling, M., "Obituary George and Esther Szekeres", Gazette of the Australian Mathematical Society, Vol 32 (2005), No 4, pp. 221–224. External links MacTutor Biography The work of George Szekeres on functional equations Keith Briggs 1911 births 2005 deaths Australian Jews Australian chemists Australian mathematicians Budapest University of Technology and Economics alumni Combinatorialists Fellows of the Australian Academy of Science Hungarian Jews 20th-century Hungarian mathematicians 21st-century Hungarian mathematicians Members of the Order of Australia University of New South Wales faculty Hungarian chemists Austro-Hungarian mathematicians Hungarian emigrants to Australia