All sales of real property for delinquent special assessments, or installments thereof, made prior to March 17, 1937, by any county auditor under section 40-25-09 hereby are declared to be valid sales notwithstanding the fact that the real property subject to sale for delinquent general taxes and delinquent special assessments, or installments thereof, were not sold separately as required by said section and notwithstanding the fact that separate certificates were not issued for the delinquent general taxes and the delinquent special assessments or installments thereof.