  The amplitudes for photoproduction of two pseudoscalars on a nucleon are
expanded in the overall c.m. frame in a model independent way with respect to
the contribution of the final state partial wave of total angular momentum $J$
and its projection on the normal to the plane spanned by the momenta of the
final particles. The expansion coefficients which are analogues to the
multipole amplitudes for single meson photoproduction contain the complete
information about the reaction dynamics. Results of an explicit evaluation are
presented for the moments $W_{jm}$ of the inclusive angular distribution of an
incident photon beam with respect to the c.m.\ coordinate system defined by the
final particles taking photoproduction of $\pi^0\pi^0$ and $\pi^0\eta$ as an
example.
