Description of the ghostwriter system, an undetectable practice until now. For example, no one has detected R. Gary behind E. Ajar. Nobody could identify the authors who wrote the plays produced by the Cardinal Richelieu. No one can say what part T. Corneille took in some plays produced by Montfleury or Hauteroche. During the seventeenth century, most of the plays were not presented by their authors but by intermediaries who negotiated them with the theater companies. An authorship attribution method by computer helps to solve these puzzles. The reliability of the method has been rigorously tested. It attributes to P. Corneille all the plays in verse produced by Molière, in addition to Dom Juan, l'Avare, le Bourgeois Gentilhomme and le Malade imaginaire. Firm historical evidence confirms these author attributions.
