@unpublished{168866,
  author = {Bo E. Honor{\'e}},
  title = {Identification Results For Duration Models With Multiple Spells Or Time{\textendash}Varying Covariates},
  year = {1990},
  url = {http://www.princeton.edu/~honore/papers/multiple_spells_earlier_version.pdf},
  language = {eng},
}