  To stress the effect of the pairing position deviating from the Fermi level,
we must investigate the pairs in the wave vector space, and then we use the
dynamic equation to study some correlation functions. This article shows that
the Fermi pocket is related to the effect of free electron states on the ARPES
experiment. This also leads us to understand why the Fermi arc appears in
Bi2212 while the Fermi pocket appears in Bi2201 with the valence bandwidth and
the work function known for them.
