REFERENCES troubles

I get this error when creating a database:

CREATE TABLE workers(
  name        varchar(30),
  firstname   varchar(30),
  id_personal decimal(10)NOT NULL UNIQUE PRIMARY KEY,
);

CREATE TABLE payements(
  date_of     date,
  owner       REFERENCES   workers(id_personal)
);


IT gimme error!!!
why this isn't right?
the postgres documentation seem say to do in this manner...
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