Boris Odehnal, Some triangle centers associated with the circles
tangent to the excircles,
Forum Geometricorum, 10 (2010) 35--40.
Abstract: We study those tritangent circles of the excircles of a triangle
which enclose exactly one excircle and touch the two others from the outside.
It turns out that these three circles share exactly the Spieker point. Moreover
we show that these circles give rise to some triangles which are in perspective
with the base triangle. The respective perspectors turn out to be new polynomial