  New features of a previously introduced Group Approach to Quantization are
presented. We show that the construction of the symmetry group associated with
the system to be quantized (the "quantizing group") does not require, in
general, the explicit construction of the phase space of the system, i.e., does
not require the actual knowledgement of the general solution of the classical
equations of motion: in many relevant cases an implicit construction of the
group can be given, directly, on configuration space. As an application we
construct the symmetry group for the conformally invariant massless scalar and
electromagnetic fields and the scalar and Dirac fields evolving in a symmetric
curved space- time or interacting with symmetric classical electromagnetic
fields. Further generalizations of the present procedure are also discussed and
in particular the conditions under which non-abelian (mainly Kac-Moody) groups
can be included.
