Author: Michal MARVAN
We present a criterion of reducibility of a zero curvature representation
to a solvable subalgebra, hence to a chain of conservation laws.
Namely, we show that reducibility is equivalent to the existence of a section
of the generalized Riccati covering.
Results are applied to conversion between Guthrie's and Olver's form of
32 pages, LaTeX-2e.
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