  A recent description of the highly viscous flow ascribes it to irreversible
thermally activated Eshelby transitions, which transform a region of the
undercooled liquid to a different structure with a different elastic misfit to
the viscoelastic surroundings. The description is extended to include
reversible Eshelby transitions, with the Kohlrausch exponent $\beta$ as a free
parameter. The model answers several open questions in the field.
