On 2D Inverse Problems/Body
the logarithmic derivative of the analitical continuation atound the origin... the monodromy of a differential operator's equation and analytical /harmonic continuation on a network/graph or a continuous domain such as complex sphere/plane...

the higher order invariants of complex domains and analytical continuation ambiguity... Several ways to calculate the highest invariants of trace of the monodromy: continued fractions zeros and poles, the cycle of submarines and the zeros of the determinant with mu-spectrum parameter... on duality and y-delta invariance...