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_63991 ( "Class" text, "Wheel arrangement" text, "Fleet number(s)" text, "Manufacturer" text, "Serial numbers" text, "Year made" text, "Quantity made" text, "Quantity preserved" text, "Year(s) retired" text )

### Question ###
What are the serial numbers for the locomotives of Class 4-8-4 oooooooo northern?

### Accurate SQL ###

SELECT "Serial numbers" FROM table_63991 WHERE "Class" = '4-8-4 — oooooooo — northern'