@article{ZNSL_2008_360_a10,
     author = {G. Panina and G. N. Khimshiashvili},
     title = {Cyclic polygons are critical points of area},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {238--245},
     publisher = {mathdoc},
     volume = {360},
     year = {2008},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_2008_360_a10/}
}