1. S. Weinberg: Physica A 96 (1979) 327.
2. J. Gasser and H. Lentwyler: Ann. of Phys. 158 (1984) 142.
3. J. Gasser and H. Leutwyler: Nucl. Phys. B 250 (1985) 465.
4. G. Ecker: Chiral Symmetry, hep-ph/9805500. A. Pich: Effective Field Theory, hep-ph/9806303. U.-G. Meißner: Chiral Nucleon Dynamics, in Themes in Strong Interactions (Ed. J.L. Goity), World Scientific, Singapore, 1998, p. 139. B.R. Holstein: Introduction to Chiral Perturbation Theory, in Hadronic structure (Ed. J.L. Goity), World Scientific, Singapore, 1998, p. 58.
5. B. Holstein: Am. J. Phys. 67 (1999) 422.