  We consider skew-symmetric operators $A_{0}$ on a Hilbert space $H$ and
characterise all (nonlinear) m-accretive restrictions of $A:=-A_{0}^{\ast}$ in
terms of the "deficiency spaces" $\ker(1\pm A)$. The results are illustrated by
several examples and applied to a partial differential equation with an
impedance type boundary condition.
