1. Acheson, R. M., Kemp, F. H. and Parfit, J. 1955. Height, weight and skeletal maturity in the first five years of life. Lancet, i, 691.
2. Barron, S. L. and Vessey, M. P. 1966. Birth weight of infants born to immigrant women. Brit. J. prev. soc. Med., 20, 127.
3. Brimblecombe, R. S. W., Ashford, J. R. and Fryer, J. G. 1968. The significance of low birth-weight in perinatal mortality: A study of variations within England and Wales. Brit J. prev. soc. Med., 22, 27.
4. Bulmer, M. G. 1970. The Biology of Twinning in Man. Clarendon Press, Oxford.
5. Butler N. R. and Bonham, D. G. 1963. Perinatal Mortality. The first report of the 1958 British Perinatal Mortality Survey. Edinburgh, E. & S. Livingstone Ltd.