  A subtractionless method for solving Fermi surface sheets ({\tt FSS}), from
measured $n$-axis-projected momentum distribution histograms by two-dimensional
angular correlation of the positron-electron annihilation radiation ({\tt
2D-ACAR}) technique, is discussed. The window least squares statistical noise
smoothing filter described in Adam {\sl et al.}, NIM A, {\bf 337} (1993) 188,
is first refined such that the window free radial parameters ({\tt WRP}) are
optimally adapted to the data. In an ideal single crystal, the specific jumps
induced in the {\tt WRP} distribution by the existing Fermi surface jumps yield
straightforward information on the resolved {\tt FSS}. In a real crystal, the
smearing of the derived {\tt WRP} optimal values, which originates from
positron annihilations with electrons at crystal imperfections, is ruled out by
median smoothing of the obtained distribution, over symmetry defined stars of
bins. The analysis of a gigacount {\tt 2D-ACAR} spectrum, measured on the
archetypal high-$T_c$ compound $YBa\sb{2}Cu\sb{3}O\sb{7-\delta}$ at room
temperature, illustrates the method. Both electronic {\tt FSS}, the ridge along
$\Gamma X$ direction and the pillbox centered at the $S$ point of the first
Brillouin zone, are resolved.
