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Published online by Cambridge University Press: 09 April 2009
We give several general implicit function and closed graph theorems for ser-valued functions. Let Z be a normed space, X, Y metric spaces with X complete. Let f: X ⇉ Z, F: X × Y ⇉ Z be multifunctions with z0 ∈ f(x0) ∩ F(x0, y0) such that f is open at (x0, y0) and f ‘approximates’ F in an appropriate sense. Suppose that f−1(z) is closed, F(x, y) is compact for each x, y and z and suppose that F(x0, ·) is lower semi-continuous at y0. Then F(·, y) is of closed graph ‘locally’, is open at x0, and there exists a function x(·) with x(y) → x0 for y → y0 such that z0 ∈ F(x(y), (y)) for all y near y0. A more general form dealing with the non-linear rate situation is also established.