Table schema:
CREATE TABLE table_name_50 (riaa_sales_certification VARCHAR, billboard_200_peak VARCHAR, year VARCHAR)

Question: Before the Year 1972, what RIAA Sales Certification was awarded to the song that had a Billboard 200 Peak less than 18?
SQL: SELECT riaa_sales_certification FROM table_name_50 WHERE billboard_200_peak < 18 AND year < 1972