  The paper derives a relation for the viscosity of undercooled liquids on the
basis of the pragmatical model concept of Eshelby relaxations with a finite
lifetime. From accurate shear relaxation data in the literature, one finds that
slightly less than half of the internal stresses relax directly via single
Eshelby relaxations; the larger part dissolves at the terminal lifetime, which
is a combined effect of many Eshelby relaxations.
