The prefactor for screened Mott hopping
  The universal curve for the crossover from ES to screened Mott hopping is used to explain a reported discrepancy between the hopping conductivity prefactors in the two regimes. The prefactor in the screened Mott hopping regime is shown to vary exponentially with the inverse of the localization length in good agreement with recent experimental results. The constant C associated with ES hopping is shown to be equal to its theoretical value of 6.2. 
A.J. Dahm