1. W. Drechsler:Phys. Rev. D,2, 364 (1970) (referred to as I).
2. W. Drechsler andR. Suaya:Phys. Rev. D,2, 1879 (1970).
3. W. Drechsler:Ann. of Phys.,73, 257 (1972) (referred to as II).
4. W. Drechsler:K-matrix absorption model for the pion nucleon system, preprint, MPI, München (October 1972),Ann. of Phys., to be published.
5. V. D. Mur:Žurn. Ėksp. Teor. Fiz.,44, 2173 (1963);45, 1051 (1963) (English translation,Sov. Phys. JETP,17, 1458 (1963);18, 727 (1964)).