1. Reduced ratio of male to female births in several industrial countries;Devra;JAMA,1998
2. Environmental chemicals and changes in sex ratio: analysis over 250 years in Finland;Vartiannien;Environ Health Perspect,1999
3. Declining sex ratios in Canada;Bruce;Can Med Assoc,1997
4. Change in male-female ratio among newborn infants in Denmark;Moller;Lancet,1996
5. Annual report of childrens' physical and mental health in 1998: 18–19. Tokyo: The National Network of Physical and Mental Health in Japanese Children (in Japanese), 1998.