T. Popoviciu, Problem 5897, Gaz. Mat. 49 (1943)

... and Greetings from Louisiana!
Dr. Rick Mabry, Department of Mathematics Louisiana State University in Shreveport (USA)

1. The problem is cited on pp 132-133 of "Geometric Inequalities" by O. Bottema, et al, Wolters-Noordhoff Publishing, Groningen 1969.
http://www.lsus.edu/rick-mabry
2. http://www.gazetamatematica.net/?q=node/2135#comment-295
3. Rick Mabry's Knot - http://www.lsus.edu/rick-mabry
4. Rick Mabry, Flapping Polyhedra (using Mathematica and converted to the animation with LiveGraphics3D, by M.Kraus)- http://www.lsus.edu/sc/math/rmabry/live3d/flappers.html

Note
- Gazeta Matematica, SSMR: http://www.gazetamatematica.net
- The Mathematical Association of America: http://www.maa.org/
- The American Mathematical Society (AMS): http://www.ams.org/home/page
- MathSciNet : http://www.ams.org/mathscinet/
- Gazette of the Australian Mathematical Society: http://www.austms.org.au/Gazette