Maria Flavia Mammana, Biagio Micale, and Mario Pennisi,
The Droz-Fanry circles of a convex quadrilateral,
Forum Geometricorum, 11 (2011) 109--119.
Abstract. The Droz-Farny circles of a triangle are a pair of circles of equal radii obtained by particular geometric constructions. In this paper we deal with the problem to see whether and how analogous properties of concyclicity hold for convex quadrilaterals.
[ps file] [pdf]