"Partial wave analysis in K matrix formalism" by S.U. Chung, J. Brose, R. Hackmann, E. Klempt, S. Spanier, C. Strassburger, (Mainz U., Inst. Phys. & Brookhaven & Bonn U.): 1995. Published in Annalen Phys.4:404-430,1995. eprint
"A Primer on K-matrix Formalism" by S.U. Chung, E. Klempt: Version VII (1995). electronic version available here.