Experimental fitting to the bipolaronic model of the normal-state   resistance of Bi_2Sr_2CaCu_2O_8 single crystals
  Normal-state resistance data from Bi_2Sr_2CaCu_2O_8 single crystals were fitted to the (bi)polaronic conduction model, $R=R_0 (T+\sigma_b T^2)/(1+bT)$, with satisfactory agreement over a wide temperature range. The fluctuating conduction region is found to be much narrower than that in the usual sense, as is the case for a charged Bose-gas. We estimate the effective (bi)polaron mass to be ~ 4m_e. 
Weimin Chen, J. P. Franck, and J. Jung