Structure of T- and S-matrices in unphysical sheets and resonances in   three-body systems
  Algorithm, based on explicit representations for the analytic continuation of Faddeev components of the three-body T-matrix in unphysical energy sheets, is employed to study mechanism of disappearance and formation of the Efimov levels of the helium ^4He trimer. 
A. K. Motovilov, E. A. Kolganova