On characterizations of unique extremality ✩

In this paper, we make some further considerations of the characteristic conditions of (infinitesimally) unique extremality for Beltrami coefficients obtained by Bozin et al., and find some sufficient conditions simpler in form for a Beltrami coefficient μ with nonconstant absolute value to be (infinitesimally) uniquely extremal.  2002 Elsevier Science (USA). All rights reserved.