Обсуждение: Referencing

Hi.
Is there a way to references dynamic tables? I.E:
I have a table called "buy" that create some records in "financial" table, but
there is other table called "send" that create other records in "financial".
"Financial" table have the moneys' movements and needs to be referenciable by
"buy or send". IE:create table buy ( id serial primary key, product_id integer,--references.... value money);create
tablesend ( id serial primary key, product_id integer, --references... value money);create table financial( id serial
primarykey, cred_deb smallint, value money, references integer, --<<-HERE IS THE PROBLEM, it will reference to buy OR
send
table);
Well, I dont know if I was clean.
Thank you.