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_30011_2 ( reference VARCHAR, type_and_usage VARCHAR )

### Question ###
What is every reference for type and usage of Germanium small-signal RF transistor?

### Accurate SQL ###

SELECT reference FROM table_30011_2 WHERE type_and_usage = "Germanium small-signal RF transistor"