What is the ISBN of Petit Robert?

There is no single ISBN for "Petit Robert". Petit Robert is a series of dictionaries published by Dictionnaires Le Robert, and each edition of each dictionary will have its own unique ISBN.

To find the ISBN of a specific Petit Robert dictionary, you will need to know:

* The title of the dictionary (e.g., Petit Robert Dictionnaire de la Langue Française)

* The year of publication

* The edition number (if applicable)

Once you have this information, you can search for the ISBN online using a website such as Amazon or Goodreads.