Strange Error, with unique key

I pasted here, from the begining of the database creation for explain it:

[xpy@furtab xpy]$ dropdb laboratorio
DROP DATABASE
[xpy@furtab xpy]$ createdb laboratorio
CREATE DATABASE
[xpy@furtab xpy]$ psql laboratorio
Welcome to psql, the PostgreSQL interactive terminal.

Type:  \copyright for distribution terms
       \h for help with SQL commands
       \? for help on internal slash commands
       \g or terminate with semicolon to execute query
       \q to quit

laboratorio=> CREATE TABLE PESSOA_RESPONSAVEL
laboratorio-> (
laboratorio(>   PESSOA                INTEGER NOT NULL,
laboratorio(>   CODIGO_CONSELHO       VARCHAR,
laboratorio(>   ESPECIALIDADE         INTEGER NOT NULL,
laboratorio(>  PRIMARY KEY (PESSOA, ESPECIALIDADE)
laboratorio(> );
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index
'pessoa_responsav
el_pkey' for table 'pessoa_responsavel'
CREATE
laboratorio=> CREATE TABLE RESULTADO_EXAME
laboratorio-> (
laboratorio(>   NR_PEDIDO     INTEGER NOT NULL,
laboratorio(>   EXAME         INTEGER NOT NULL,
laboratorio(>   SEQUENCIA     SMALLINT NOT NULL,
laboratorio(>   RESULTADO     MONEY,
laboratorio(>   PESSOA        INTEGER NOT NULL,
laboratorio(>  PRIMARY KEY (NR_PEDIDO, EXAME, SEQUENCIA)
laboratorio(> );
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index
'resultado_exame_
pkey' for table 'resultado_exame'
CREATE
laboratorio=> ALTER TABLE RESULTADO_EXAME ADD FOREIGN KEY (PESSOA)
REFERENCES PE
SSOA_RESPONSAVEL (PESSOA);
NOTICE:  ALTER TABLE will create implicit trigger(s) for FOREIGN KEY
check(s)
ERROR:  UNIQUE constraint matching given keys for referenced table
"pessoa_respo
nsavel" not found
laboratorio=>

Anyone knows what is this error about?
If I am right this pessoa_respons�vel is already a unique key (pk).

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