Circles (A40a), (A40b), (A40c), and (A40d): The Outside Powerian Pairs
Definition
The pairs of congruent circles tangent to each other at the points of tangency of the common tangent
of (O1) and (O2) and to the circles with centers A and B passing through C
are Archimedean and form two Powerian pairs. [van Lamoen, 2007]
