1. Life expectancy m Down syndrome;Baird;J Pediatr,1987
2. International classification of diseases diagnostic codes;World Health Organisation,1977
3. Health Surveillance Registry. Measuring birth defects and handicapping disorders in the population. the British Columbia Health Surveillance Registry;Baird;Can Med Assoc J,1987
4. The incidence of Down syndrome over a 19-year period;Baird;J Med Genet,1984
5. Maternal age and Down syndrome: age-specific incidence rates by single year intervals;Trimble;Am J Med Genet,1978