SQL command join question

Hi,

I have three tables t1(a, b, c, d), t2(a, b, c, k), and t3(c, e). I need to
outer join them as shown below, but only have all tuples from t1 as output.
But the following syntax does not allow me to do so.

SELECT t1.*
FROM (t1 outer join t2 on (t1.a=t2.a and t1.b=t2.b)) t outer join t3 on
(t1.c=t3.c);

I'm getting the following error message:
ERROR: invalid reference to FROM-clause entry for table "t1"
HINT: There is an entry for table "t1", but it cannot be referenced from
this part of the query.

I'll be grateful if someone may help me with this.

Thanks,
Ehab

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