Theorem 5.10.
Assuming that:
A
U
be as above
J
=
ℕ
{
C
⊆
ℕ
:
ℕ
∖
C
is finite
}
⊆
U
n
∈
ℕ
for each
m
∈
ℕ
, let
B
m
⊆
A
n
satisfying:
(1)
[
B
m
]
≠
∅
∀
m
∈
ℕ
(2)
[
B
k
]
⊆
[
B
m
]
for all
m
,
k
∈
ℕ
with
m
≤
k
Then
⋂
m
∈
ℕ
[
B
m
]
≠
∅
.