<prompt> Recording of data of bihs and deaths in a community continuously after 6 months survey is known asSample registration systemData linkageHospital recordsNotification system  <response>: Sample registration system Sample Registration system SRS - staed in 1960 SRS provide reliable estimated of bih rate at national and state levels. It is dual record system Enumerator : Continuous enumeration of bih and death rate. - Independent survey : Survey every 6 month by investigator supervisor. It cover entire country major source of death information. Census : It taken usually at intervals of 10 year Civil Registration system : It is deficient in India. Estimation to missing event by enumerator and supervisor using well defined technique know as CHANDRASEKHARAN DEMMY FORMULA 