Lemma 5.1.
Assuming that:
c
>
0
is such that
h
(
x
y
)
≥
c
(
x
h
(
y
)
+
y
h
(
x
)
)
for every
x
,
y
∈
[
0
,
1
]
A
is a family of sets such that every element (of
⋃
A
) belongs to fewer than
p
|
A
|
members of
A
Then
H
[
A
∪
B
]
>
c
(
1
−
p
)
(
H
[
A
]
+
H
[
B
]
)
.