Authors: O. V. Efimovskaya, V. V. Sokolov
Decompositions of the loop algebra over so(4) are
considered, and the exactly integrable nonlinear hyperbolic systems of
the principal chiral field equation type are analyzed. New example of
such system is found and the Lax representation for this example
10 pages, AmS-LaTeX (LaTeX-2e).
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