SQL PLUS(ORACLE)

I NEED help trying to get my foreign key to compile.

Check my code on the tables, please let me know what is wrong here:

CREATE TABLE REP( REP_ID char(3), REP_LNAME varchar(20) NOT NULL,

REP_FNAME varchar(20) NOT NULL, REP_STREET char(15), REP_CITY varchar(20) NOT NULL,

REP_STATE char(2), REP_ZIP char(5), REP_COMM decimal(7,2),

REP_RATE decimal(2,2),PRIMARY KEY(REP_ID));

CREATE TABLE CUSTOMER( CUST_ID char(4), CUST_NAME varchar(50) NOT NULL,

CUST_STREET char(20), CUST_CITY varchar(20) NOT NULL, CUST_STATE char(2),

CUST_ZIP char(5), CUST_BALANCE decimal(7,2), CUST_LIMIT decimal(7,2),

PRIMARY KEY(CUST_ID),

FOREIGN KEY(REP_ID) REFERENCES REP);

CREATE TABLE PRODUCT( PROD_ID char(5), PROD_DESC varchar(30) NOT NULL,

PROD_QUANTITY char(3), PROD_TYPE char(2), PROD_WAREHOUSE char(1), 

PROD_PRICE decimal(5,2),

PRIMARY KEY(PROD_ID);

CREATE TABLE INVOICE( INVOICE_NUM char(5), INVOICE_DATE DATE,

FOREIGN KEY(CUST_ID) references CUSTOMER(CUST_ID));

CREATE TABLE LINE (LINE_NUM_ORDERED char(2), LINE_PRICE decimal(5,2),

FOREIGN KEY(INVOICE_NUM) references INVOICE(INVOICE_NUM));

FOREIGN KEY(PROD_ID) references PRODUCT(PROD_ID));