In passato ho contattato personalmente il creatore di STRATA in merito all'algoritmo implementato per il metodo FD-EQL
questa è stata la sua risposta:

The frequency dependent EQL method that is included in Strata is basedon Kausel and Assimaki (2002). I have attached one of the journal articles. I have checked my implementation of the method, but I have done much testing of the method in general. I would consider the method to be experimental.