@conference{18873,
  author = {Macmahon S},
  title = {Role of observational epidemiology in clinical trials},
  year = {2005},
  journal = {10th International Symposium on Long-term Clinical Trials, Advanced Issues in the Design and Conduct of Randomised Clinical Trials},
  month = {91732177550},
  address = {Oxford, UK},
  language = {eng},
}