You are referring (no doubt) to the ANSI/ISO SQL Standard.
The papers are $18 each from ANSI in pdf format (or they were when I bought them some time ago).
There are draft versions scattered about on the internet for free.
This looks like a set of them:
http://www.cse.iitb.ac.in/dbms/Data/Papers-Other/SQL1999/
From: pgsql-hackers-owner@postgresql.org [mailto:pgsql-hackers-owner@postgresql.org] On Behalf Of Benjamin Arai
Sent: Friday, January 14, 2005 2:51 PM
To: pgsql-hackers@postgresql.org
Subject: [HACKERS] PostgreSQL Specification
I asked this question a while back and I got an answer but I lost it.
Where can I get a copy of the SQL specification that PostgreSQL follows? Who ever answered, as I recall said it was not free if that is any help.
Benjamin