<s>
A	O
Sparse	B-Error_Name
graph	I-Error_Name
code	I-Error_Name
is	O
a	O
code	O
which	O
is	O
represented	O
by	O
a	O
sparse	O
graph	O
.	O
</s>
<s>
The	O
state	O
of	O
the	O
art	O
classical	O
error-correcting	B-Error_Name
codes	I-Error_Name
are	O
based	O
on	O
sparse	O
graphs	O
,	O
achieving	O
close	O
to	O
the	O
Shannon	O
limit	O
.	O
</s>
<s>
The	O
archetypal	O
sparse-graph	O
codes	O
are	O
Gallager	O
's	O
low-density	B-Error_Name
parity-check	I-Error_Name
codes	I-Error_Name
.	O
</s>
