  Quantum and classical physical states are represented in a unified way when
they are described by symplectic tomography. Therefore this representation
allows us to study directly the necessary conditions for a classical universe
to emerge from a quantum state. In the previous study on the de Sitter universe
this was done by comparing the classical limit of the quantum tomograms with
the tomograms resulting from the classical cosmological equations. In this
paper we first review these results and extend them to all the de Sitter
models. We show further that these tomograms can be obtained directly from
transposing the Wheeler-De Witt equation to the tomographic variables.
Subsequently, because the classic limits of the quantum tomograms are
identified with their asymptotic expressions, we found the necessary conditions
to extend the previous results by taking the tomograms of the WKB solutions of
the Wheeler-DeWitt equation with a any potential. Furthermore in the previous
works we found that the de Sitter models undergo the quantum-to-classical
transition when the cosmological constant decays to its present value, we
discuss at the end how far we can extend this result to more general models. In
the conclusions, after discussing any improvements and developments of the
results of this work, we sketch a phenomenological approach from which to
extract information about the initial states of the universe.
