  As an extension of the Ivanov-Zupnik approach to self-dual nonlinear
electrodynamics in four dimensions [1,2], we reformulate U(1) duality-invariant
nonlinear models for a gauge $(2p-1)$-form in $d=4p$ dimensions as field
theories with manifestly U(1) invariant self-interactions. This reformulation
is suitable to generate arbitrary duality-invariant nonlinear systems including
those with higher derivatives.
