  For deuteron photo- and electrodisintegration the selection of complete sets
of polarization observables is discussed in detail by applying a recently
developed new criterion for the check of completeness of a chosen set of
observables. The question of ambiguities and their resolution by considering
additional observables is discussed for a numerical example, for which the role
of experimental uncertainties is also investigated. Furthermore, by inversion
of the expressions of the observables as hermitean forms in the $t$-matrix
elements a bilinear term of the form $t_{j'}^*t_j$ can be given as a complex
linear form in the observables from which an explicit solution for $t_j$ in
terms of observables can be obtained. These can also be used to select sets of
observables for the explicit representation of the $t$-matrix.
