We present the results of a nonlinear iterative inverse analysis of
the hydrostatic spherically-symmetric component of the solar internal
structure using p-mode frequencies from the observational data sets now
available. The technique which we use is based on the "quasi-asymptotic"
description of solar p-modes developed by Roxburgh and Vorontsov (1996).
As a significant improvement of the standard asymptotic analysis, this
description incorporates Born approximation to allow a detailed treatment
of the regions of rapid variation of seismic parameters with depth (base
of the convection zone) and strong influence of gravity perturbations
(low-degree modes which penetrate deep into the solar core). The primary
target of our analysis is to achive the highest possible resolution of
the region around the base of the solar convection zone, for searching
possible signatures of penetrative convection, element diffusion and/or
strong magnetic fields. Preliminary results for global inversion are also
presented.