Remark 3.2.28
For the difference of sets, neither the commutative law nor the
associative law hold. Figures
and
give a counterexample to the associative law.
Figure 14:
A counterexample to the associative law: first part.

Figure 15:
A counterexample to the associative law: second part.

Here is another example: let
be the set of all integers
such
that
. Let
,
and
. Then
we have: