translate English to French: This is particularly so where the classification of imports is very difficult, if not impossible, taking into account the heading, the Explanatory Notes, etc. as they were at the time of importation.
Cela est particulièrement vrai lorsque le classement des importations est très difficile, sinon impossible, compte tenu des termes de la position, des Notes explicatives, etc., tels qu'ils existaient au moment de l'importation.