  This paper presents a comprehensive review of the wave-function approach for
derivation of the number-resolved Master equations, used for description of
transport and measurement in mesoscopic systems. The review contains important
amendments, clarifying subtle points in derivation of the Master equations and
their validity. This completes the earlier works on the subject. It is
demonstrated that the derivation does not assume weak coupling with the
environment and reservoirs, but needs only high bias condition. This condition
is very essential for validity of the Markovian Master equations, widely used
for a phenomenological description of different physical processes.
