CREATE TABLE table_31422 ("Prefix class" TEXT, "Type and usage" TEXT, "Example" TEXT, "Equivalent" TEXT, "Reference" TEXT)

What is every reference for type and usage of Germanium small-signal RF transistor?
SELECT "Reference" FROM table_31422 WHERE "Type and usage" = 'Germanium small-signal RF transistor'
SELECT "Reference" FROM "table_31422" WHERE "Type and usage" = 'Germanium small-signal RF transistor'