Martin Josefsson

On the classification of convex quadrilaterals

Further characterisations of tangential quadrilaterals

101.38 Metric relations in crossed cyclic quadrilaterals

Properties of bisect-diagonal quadrilaterals

Minimal area of a bicentric quadrilateral

Metric relations in crossed trapezia

The importance of characterisations in geometry

101.36 On the area of a tangential quadrilateral

Generalisation of a quadrilateral duality theorem

100.30 Generalisations of the altitude theorem