If is Meromorphic in a region enclosed by a curve , let be the number of
Complex Roots of in , and be the number of Poles
in , then
See also Variation of Argument
Duren, P.; Hengartner, W.; and Laugessen, R. S. ``The Argument Principle for Harmonic Functions.''
Math. Mag. 103, 411-415, 1996.