query help

hi i am trying to execute the following query:

select source,(b.source/c.total),(select count(*) from entries b where
source = a.source) as source,(select count(*) from entries c) as total from
entries a group by source;

it says
ERROR: Relation "b" does not exist

the query:
select source,(select count(*) from entries where source = a.source) as
source,(select count(*) from entries) as total from entries a group by
source;

works fine but i want to use the result from source and entries to work out
a percentage in the sql query
could someone point me in the right direction?

Thanks!

Rob