Any change in the mark or any expansion in the list of goods or services must be made through a new filing. Article 17 Taking into consideration the requirements of the international agreements signed by the republic of Tunisia, the foreigner who is not a national and not a resident of Tunisia shall benefit by the provisions of this law provided that the submits proof that he legally filed or registered the mark in his country of residence or citizenship and that the said country offers reciprocal treatment with respect to the protection of Tunisian marks. Article 18 The said priority right in the international agreements ratified by the Republic of Tunisia shall cover all marks filed in a foreign country. Taking into consideration the requirements of the international agreements ratified by the Republic of Tunisia, the priority right is conditional on reciprocal treatment offered to filed Tunisian marks by the said country. Article 19 Claiming priority associated with a prior foreign filing shall require filing an authenticated true copy issued by the industrial property authority in the country where filing took place and where applicable submitting justification for the right to claiming priority to the industrial property authority within three months following the filing date in Tunisia. If this condition is not satisfied, the claim for priority shall be considered as null and void. Article 20 Any applicant who did not abide by the deadlines stipulated in articles 16 and 19 of this law, if he proves that he has a legitimate excuse may be exempted from the lapse of the right which he was liable to be subjected to, by submitting a request to the legal representative of the industrial property authority. The request shall not be accepted if: - It is not preceded by carrying out the procedures, which has been ignored. - It is filed after two months as of the termination of the impediment. - It is not accompanied by proof of payment of the due fees. Chapter Three Rights Conferred By Registration Article 21 The registration of the mark shall confer on its holder the right to own this mark with respect the goods or services indicated at the time of filing.