thm 6.1: restated conditions

the \mathfrak{S} that was here before should only contain poles of M,
but by a running assumption also contained the zeros of R (where B is
not a basis), also the statement of the thm is more self contained now,
and some more notation is recalled.
thm 6.4: small restatement

make consistent with thm 6.1, take out \mathfrak{Z}