  Applicability of anisotropic flow measurement techniques and their extension
for detectors with non-uniform azimuthal acceptance are discussed. Considering
anisotropic flow measurement with two and three (mixed harmonic) azimuthal
correlations we introduce a set of observables based on the x and y components
of the event flow vector. These observables provide independent measures of
anisotropic flow, and can be used to test self-consistency of the analysis.
Based on these observables we propose a technique that explicitly takes into
account the effects of non-uniform detector acceptance. Within this approach
the acceptance corrections, as well as parameters which define the method
applicability, can be determined directly from experimental data. For practical
purposes a brief summary of the method is provided at the end.
