On a theorem by Leon Greenberg
A. W. Mason · Proceedings of the American Mathematical Society · 1969
Any parabolic matrix in r is one for which the trace is + 2, and 9 has a complete system of t, say, parabolic representatives, P1, * * Pt, which have the properties that any parabolic element of 9 is conjugate in 9 to a power of one of the Pi and no nontrivial power of Pi is conjugate in to a power of Pi (1 1,