The bound state problem is considered within the framework of the Bethe-Salpeter (BS) equation in the ladder model. The bound state are composed of a fermion and an antifermion of equal mass $m$ interacting through the exchange of a massless vector particle. Spectral properties of the coupling constant as a function of the bound state mass \(E\) (\( 0\leq E<2m\)) are clarified. Global views are obtained connecting the Goldstein problem (the appearance of continuous spectra in the spinor-spinor BS equation) with the abnormal solutions in the Wick- Cutkosky model (the scalar-scalar BS equation).

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