Bojan Hvala, Diophantine Steiner triples and Pythagorean-type
Forum Geometricorum, 10 (2010) 93--97.
Abstract: We present a connection between Diophantine Steiner triples (integer
triples related to configurations of two circles, the larger containing the
smaller, in which the Steiner chain closes) and integer-sided triangles with
an angle of 60, 90 or 120 degrrees. We introduce an explicit formula
and provide a geometrical interpretation.