The original version of this article unfortunately contained three minor text errors. The sets of points satisfying the conditions r0 = 0 and r3 = i3 = 0 are branch points of the Green function, not poles as is written in the text. Therefore these points do not represent resonances or bound states. They were not effectively considered in the analysis and do not have any impact on the conclusions.The sentences: "If r0 = 0, there is a pole, representing a resonance in N(e')". (page 3); "... or r0 = 0. For e' > 1 it must hold r3 = i3 = 0 in order to be a pole." (page 4); "... (including that for r0 )" (page 5).should be removed to make the text correct. These should be considered mere text errors (due to a failure in the revision of a preliminary version of the text). Therefore, the simple omission of the sentences mentioned above is enough to correct the article.
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