Create table with Fk

I'm having trouble creating a table with several Foreign keys

The tables are the following

CREATE TABLE tbl_Autor(

nAutorID INT AUTO_INCREMENT PRIMARY KEY NOT NULL UNIQUE,
cNombre VARCHAR(20),
cApellidos VARCHAR(50)
);

CREATE TABLE tbl_Libro(

nLibroID INT AUTO_INCREMENT PRIMARY KEY NOT NULL UNIQUE,
cTitulo VARCHAR(20),
nAnyoPublicacion DATE,
nEditorial INT,
CONSTRAINT fk_Editorial FOREIGN KEY(nEditorial) REFERENCES tbl_Editorial(nEditorialID)
ON DELETE SET NULL

);

and this is the one that gives me problems

CREATE TABLE tbl_LibroAutor(

nLibroID INT,
nAutorID INT,
CONSTRAINT pk_LibroAutor PRIMARY KEY(nLibroID, nAutorID),
CONSTRAINT fk_Libro FOREIGN KEY(nLibroID) REFERENCES tbl_Libro(nLibroID)
ON DELETE SET NULL,
CONSTRAINT fk_Autor FOREIGN KEY(nAutorID) REFERENCES tbl_Autor(nAutorID)
ON DELETE SET NULL
);