Zvonko Cerin, Rings of squares around orthologic triangles,
Forum Geometricorum, 9 (2009) 57--80.
Abstract: We explore some properties of the geometric configuration
when a ring of six squares with the same orientation are erected on the segments
BD, DC, CE, EA, AF and FB connecting the vertices of two orthologic triangles
ABC and DEF. The special case when DEF is the pedal triangle of a variable
point P with respect to the triangle ABC was studied earlier by Bottema,
Deaux, Erhmann and Lamoen, and Sashalmi and Hoffmann. We extend their results
and discover several new properties of this interesting configuration.