Equichordal point problem information

In Euclidean plane geometry, the equichordal point problem is the question whether a closed planar convex body can have two equichordal points.^[1] The problem was originally posed in 1916 by Fujiwara and in 1917 by Wilhelm Blaschke, Hermann Rothe, and Roland Weitzenböck.^[2] A generalization of this problem statement was answered in the negative in 1997 by Marek R. Rychlik.^[3]

^ Victor Klee; Stan Wagon (1991), Old and New Unsolved Problems in Plane Geometry and Number Theory, Mathematical Association of America, ISBN 978-0-88385-315-3
^ W. Blaschke, H. Rothe, and R. Weitzenböck. Aufgabe 552. Arch. Math. Phys., 27:82, 1917
^ Marek R. Rychlik (1997), "A complete solution to the equichordal point problem of Fujiwara, Blaschke, Rothe and Weitzenböck", Inventiones Mathematicae, 129 (1): 141–212, Bibcode:1997InMat.129..141R, doi:10.1007/s002220050161, S2CID 17998996

[problems-geometry-1] Victor Klee; Stan Wagon (1991), Old and New Unsolved Problems in Plane Geometry and Number Theory, Mathematical Association of America, ISBN 978-0-88385-315-3

[Blaschke-2] W. Blaschke, H. Rothe, and R. Weitzenböck. Aufgabe 552. Arch. Math. Phys., 27:82, 1917

[The_Proof-3] Marek R. Rychlik (1997), "A complete solution to the equichordal point problem of Fujiwara, Blaschke, Rothe and Weitzenböck", Inventiones Mathematicae, 129 (1): 141–212, Bibcode:1997InMat.129..141R, doi:10.1007/s002220050161, S2CID 17998996