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_name_51 ( call_sign VARCHAR, city_of_license VARCHAR )

### Question ###
What is Call Sign, when City of License is Brownfield, Texas?

### Accurate SQL ###

SELECT call_sign FROM table_name_51 WHERE city_of_license = "brownfield, texas"