RE:REFERENCES

I am sorry what I am trying is:

>CREATE TABLE purchase (id int, po int, date date, PRIMARY KEY (id));
>
>CREATE TABLE lcopen (lc numeric, po int, PRIMARY KEY (lc));

replace with:
CREATE TABLE lcopen (lc numeric, po int REFERENCES purchase (po), PRIMARY KEY (lc));
but there is an error and I do not how to correct that.

>
>CREATE TABLE lcreceive (
>   id int,
>   lc numeric REFERENCES lcopen(lc),
>   purid int REFERENCES purchase(id)
>)
>;
>
>I think this is what you are asking this will effectively make lc and
>purid in lcreceive foreign keys of the other tables
>
>Darren Ferguson
>
>On Sun, 10 Mar 2002, [big5] ngterry wrote:
>
>>
>> Hi!
>>
>> I am just a newbie in postgresql.  What if:
>>
>> CREATE TABLE purchase (id int, po int, date date, PRIMARY KEY (id));
>>
>> CREATE TABLE lcopen (lc numeric, po int, PRIMARY KEY (lc));
>>
>> CREATE TABLE lcreceive (id int, lc numeric REFERENCES lcopen, purid int REFERENCES purchase);
>>
>> How do I refer the keywords po in table lcopen to table purchase the po keywords?  I am quite confuse, since I have
announceid in table purchase as PRIMARY KEY.  I do not know how to key another keywords. 
>>
>> Best regards,
>>
>> Terence
>> ==================================================================
>> 新浪SMS短訊：http://sms.sina.com.hk
>> 給遠方親友傳上無限驚喜
>> 50MB 電子郵件 ：http://sinamail.sina.com.hk
>>
>>
>>
>>
>> ---------------------------(end of broadcast)---------------------------
>> TIP 4: Don't 'kill -9' the postmaster
>>
>
>
==================================================================
新浪SMS短訊：http://sms.sina.com.hk
給遠方親友傳上無限驚喜
50MB 電子郵件 ：http://sinamail.sina.com.hk