[CIG-SEISMO] Specfem anelasticity

[Phil Cummins]

Hi,

I am wondering if someone could please direct me to which publication 
gives a detailed treatment of how anelasticity is handled in specfem. 
 From comments in the manual and the input file I believe an absorption 
band model is used, but I couldn't find anything describing just how 
this is done. Can someone please tell me, which of the many specfem 
references might cover this?
Many thanks,

- Phil