  We emphasize the crucial r\^ ole played by non-factorizable phases in the
analysis of the Yukawa flavour structure performed in weak bases with Hermitian
mass matrices and with vanishing $(1,1)$ entries. We show that non-factorizable
phases are important in order to generate a sufficiently large $\sin 2 \beta $.
A method is suggested to reconstruct the flavour structure of Yukawa couplings
from input experimental data both in this Hermitian basis and in a
non-Hermitian basis with a maximal number of texture zeros. The corresponding
Froggatt--Nielsen patterns are presented in both cases.
