PSQL problem z foreign key

SET
CREATE TABLE
CREATE TABLE
psql: B2.sql: 29: ERROR: column "kod" referenced in foreign key constraint does not exist
CREATE TABLE

SET client_encoding = 'utf-8';

CREATE TABLE czytelnik
(
nr_karty char( 6 ) not null,
imie varchar not null,
nazwisko varchar not null,
CONSTRAINT czytelnik_pk PRIMARY KEY( nr_karty )
);
CREATE TABLE ksiazka
(
kod char( 6 ) not null,
tytul varchar not null,
cena money not null,
rok char( 4 ) not null,
wydawnictwo varchar not null,
CONSTRAINT ksiazka_pk PRIMARY KEY( kod )
);
CREATE TABLE autor
(
nr_autor char( 6 ) not null,
imie varchar not null,
nazwisko varchar not null,
CONSTRAINT autor_pk PRIMARY KEY( nr_autor ),
CONSTRAINT ksiazka_fk FOREIGN KEY( kod )
REFERENCES ksiazka( kod )
ON UPDATE CASCADE
ON DELETE SET NULL
);
CREATE TABLE egzeplarz
(
nr_inw char( 6 ) not null,
kod char( 6 ) not null,
nr_karty char( 6 ),
data date,
CONSTRAINT egzeplarz_pk PRIMARY KEY( nr_inw ),
CONSTRAINT ksiazka_fk FOREIGN KEY( kod )
REFERENCES ksiazka( kod )
ON UPDATE CASCADE
ON DELETE CASCADE,
CONSTRAINT czytelnik_fk FOREIGN KEY( nr_karty )
REFERENCES czytelnik( nr_karty )
ON UPDATE CASCADE
);