The Potential theory plays an important r61e in the modern function theory. And, so may be seen, harmonic functions play the central part
in this book. Since there are so many excellent works on function theory already, we assume as known such rudimental facts, as elementary
properties of regular and harmonic functions, normal family, Koebe's distortion theorem, etc. We also assume the definition of Riemann
surfaces as known and we make no specific mention of it.