  Bose-Einstein correlations of pairs of identical charged pions produced in
hadronic Z decays are analyzed in terms of various parametrizations. A good
description is achieved using a L\'evy stable distribution in conjunction with
a model where a particle's momentum is highly correlated with its space-time
point of production, the tau model. However, a small but significant elongation
of the particle emission region is observed in the Longitudinal Center of Mass
frame, which is not accommodated in the tau model. This is investigated using
an ad hoc modification of the tau model.
