  While closing their famous paper entitled "Pseudogap: friend or foe of
high-Tc?" Norman, Pines, and Kallin underlined that before we have a
microscopic theory, we must have a consistent phenomenology. This was in 2005.
As it turns out in 2006 a phenomenological theory of the pseudogap state was
proposed by Gor'kov and Teitel'baum. This originated from their careful
analysis of the Hall effect data, and it has been very successful model as
numerous investigations over the years has shown. In this mini-review the
essence of the idea of Gor'kov and Teitel'baum is presented. The pseudogap
obtained by them from the Hall effect data agrees very well with that obtained
from the ARPES data. This famous Gor'kov-Teitel'baum Thermal Activation model
(in short GTTA model) not only presents a consistent phenomenology of the
pseudogap state but also it rationalizes the Hall angle data and it presents a
strong case against the famous "two-relaxation times" idea of Anderson and
collaborators.
