page 16  insufficient quality and quantity to meet local demand or at prices which the Minister deems abusive or for any other reason of public interest, including anticompetitive practices, provided that: 1. the product has been introduced into commercial channels in the territory from which it is to be imported by the patent holder or with his consent; 2. the patent claiming the product or process used for its manufacture is in force in the territory from which the product is to be imported and is the property of the same person who holds the patent in Burundi or that of a person under his control. Article 60: In the event that the importer fails to meet the goal which had justified the decision of the Minister responsible for trade to consider the patent rights exhausted, the Minister shall revoke the authorization on his own initiative or at the request of the patent holder. Article 61: In the event that the conditions which have led to the Minister’s decision to consider the patent exhausted no longer obtain, the Minister may, on his own initiative or at the request of the patent holder or owner of the mark, revoke the authorization, provided that the legitimate interests of the importer are safeguarded, primarily to the effect that the importer shall retain the right to clear his stock. Section 4: Term of protection and annual fees Article 62: The patent shall expire at the end of the twentieth year as from the date of filing. If the patent is granted more than four years after the date of filing, the term of protection granted by this patent shall be automatically extended by the entire period which has elapsed as from the date of filing. Article 63: A progressive annual fee must be paid in advance to the Industrial Property Office as from the first year following the filing date of the patent application in order to maintain the patent or patent application in force. Any patentee who fails to pay his annuity on the dating of filing of his patent application shall be stripped of all his rights. Nevertheless, the patentee shall have a six-month grace period to make payment. Under these circumstances, he shall be obliged to pay a surcharge for late payment.