Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_1337525_1 ( region_1 VARCHAR, region_4 VARCHAR, complete_series VARCHAR )

### Question ###
What is the region 1 where region 4 is tba is the complete eighth series?

### Accurate SQL ###

SELECT region_1 FROM table_1337525_1 WHERE region_4 = "TBA" AND complete_series = "The Complete Eighth Series"