  We revise critically existing approaches to evaluation of thermodynamic
potentials within the Green's function calculations at finite electronic
temperatures. We focus on the entropy and show that usual technical problems
related to the multivalued nature of the complex logarithm can be overcome.
This results in a simple expression for the electronic entropy, which does not
require any contour integration in the complex energy plane. Properties of the
developed formalism are discussed and its illustrating applications to selected
model systems and to bcc iron with disordered local magnetic moments are
presented as well.
