{{Cite book| publisher = INED, CEPED| pages = 21–24| editors = Philippe Antoine, Eva Lelièvre (eds.)| last1 = Antoine| first1 = Philippe| last2 = Lelièvre| first2 = Eva| title = Fuzzy states and complex trajectories : observation, modelization and interpretation of life histories| chapter = What is fuzzy : the time, the event or the state ?| location = Paris| series = Méthodes et Savoirs| date = 2009}}