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_21312959_1 ( written_by VARCHAR, no_in_series VARCHAR )

### Question ###
Who are the writers for the episode number in series 129?

### Accurate SQL ###

SELECT written_by FROM table_21312959_1 WHERE no_in_series = 129