how to rename an unnamed uniqueness constraint?

Hello,

I have a table created with

CREATE TABLE Current_academic_year
(
    year_id        INT    REFERENCES Academic_years,
    CONSTRAINT year_id CHECK(year_id IS NOT NULL),
    active        BOOL    NOT NULL,

    UNIQUE(year_id),
    UNIQUE(active)
)
;

Now I need to drop the constraint "UNIQUE(active)".
I tried variations of

ALTER TABLE current_academic_year DROP CONSTRAINT "???"

but I didn't succeed.

I'm using version 7.4.8.

Thanks in any case for your efforts!

Oliver

P.S. The "documentation" regarding the e-mail lists is
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I'm supposed to post to a list, and/or to receive mails.
Of course I tried

http://mail.postgresql.org/mj/mj_wwwusr/domain=postgresql.org

and the help pages etc.: I always get "unsuccessful" back,
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Just one paragraph about the idea how the average *novice*
should post a question and read the answer would be quite
useful.