  We study the electron momentum distribution function (EMDF) for the
two-dimensional t-t'-J model doped with one hole on finite clusters by the
method of twisted boundary conditions. The results quantitatively agree with
our analytical results for a single hole in the antiferromagnetic background,
based on the self-consistent Born approximation (SCBA). Moreover, within the
SCBA an anomalous momentum dependence of EMDF is found, pointing to an emerging
large Fermi surface. The analysis shows that the presence of
next-nearest-neighbor (NNN) hopping terms changes EMDF only quantitatively.
