Circles and parabolas (Q1286337)

The author describes interesting properties of circles and parabolas indicating the existence of a general principle saying: Certain types of theorems on circles can be translated into true statements about parabolas. It may be helpful and yield additional insights to the matter to mention the booklet of \textit{H. Sachs}: `Ebene isotrope Geometrie', Vieweg (1987; Zbl 0625.51001), which may answer some of the questions posed in this interesting article.