Create Table Foreign key failure

I want to create 3 foreign keys in a table such as this:

DROP TABLE IF EXISTS puo;CREATE TABLE IF NOT EXISTS puo (
    ano INT ( 4 )NOT NULL,
    empresa CHAR ( 8 )NOT NULL,
    acro_proyecto CHAR ( 10 )NOT NULL,
    partida VARCHAR ( 100 ) NOT NULL,
    proveedor VARCHAR (100) NOT NULL,
    formadepago VARCHAR (100) NOT NULL,
    solicitado_por CHAR (4) NOT NULL,
    aprobado_por CHAR (4) NOT NULL,
    puo VARCHAR ( 50 )NOT NULL,
    posicion VARCHAR (59) NOT NULL,
    producto_servicio VARCHAR ( 150 ) NOT NULL,
    cantidad INT NOT NULL,
    precio_unitario VARCHAR ( 10 ) NOT NULL,
    descuento_porcentaje VARCHAR ( 10 ) NOT NULL,
    iva VARCHAR ( 10 ) NOT NULL,
    precio_total VARCHAR ( 20 ) NOT NULL,
    descuento VARCHAR ( 20 ) NOT NULL,
    precio_uni_descuento VARCHAR ( 20 ) NOT NULL,
    iva_total VARCHAR ( 20 ) NOT NULL,
    total VARCHAR ( 20 ) NOT NULL,
    fecha TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
    PRIMARY KEY(puo),
    FOREIGN KEY (empresa) REFERENCES compania(acronimo) on DELETE CASCADE,
    FOREIGN KEY (solicitado_por) REFERENCES autorizados(acro_usuario) on DELETE CASCADE,
    FOREIGN KEY (aprobado_por) REFERENCES usuarios(acro_usuario) on DELETE CASCADE,
    FOREIGN KEY (acro_proyecto) REFERENCES proyectos(acro_proyecto) on DELETE CASCADE)
            Engine = INNODB

And I miss this line:

FOREIGN KEY (solicitado_por) REFERENCES autorizados(acro_usuario) on DELETE CASCADE,

To create the foreign keys, use these tables:

DROP TABLE IF EXISTS autorizados;CREATE TABLE IF NOT EXISTS autorizados (
    acro_usuario CHAR ( 4 )NOT NULL,
    nombre VARCHAR ( 15 )NOT NULL,
    apellidos VARCHAR ( 50 )NOT NULL,
    area_ui VARCHAR ( 30 )NOT NULL,
    email VARCHAR ( 50 )NOT NULL,
    empresa CHAR ( 8 ),
    fecha TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
    PRIMARY KEY(acro_usuario),
    FOREIGN KEY (empresa) REFERENCES compania(acronimo) on DELETE CASCADE)

DROP TABLE IF EXISTS compania;CREATE TABLE IF NOT EXISTS compania (
    acronimo CHAR ( 8 ),    
    compania VARCHAR ( 50 )NOT NULL,
    fecha TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP, 
    PRIMARY KEY(acronimo))

I use two different user tables because each one is focused to perform different functions