Which trigger execute which function?

Previous DBA create a lot of triggers and functions without
documentation like:

CREATE TRIGGER trigger_name [BEFORE | AFTER] event ON table_name
FOR EACH ROW EXECUTE PROCEDURE function_name();

Now he is gone. I couldn't find his PL/PGSQL source codes!

I can do

SELECT * FROM pg_proc;
SELECT * FROM pg_trigger;

to list all the name of triggers and functions. But I don't know which
trigger
execute which function. How do I find out that?

Our USENET new server (NNTP) doesn't have comp.databases.postgresql.*
news groups. Therefore, please cc: a copy to me if you reply.
Thank Q very much in advance!