(1) The buyer may declare the contract avoided:
(a) if the failure by the seller to perform any of his obligations under the contract or this Convention amounts to a fundamental breach of contract; or
(b) in case of non-delivery, if the seller does not deliver the goods within the additional period of time fixed by the buyer in accordance with paragraph (1) of article 47 or declares that he will not deliver within the period so fixed.
(2) However, in cases where the seller has delivered the goods, the buyer loses the right to declare the contract avoided unless he does so:
(a) in respect of late delivery, within a reasonable time after he has become aware that delivery has been made;
(b) in respect of any breach other than late delivery, within a reasonable time:
(i) after he knew or ought to have known of the breach;
(ii) after the expiration of any additional period of time fixed by the buyer in accordance with paragraph (1) of article 47, or after the seller has declared that he will not perform his obligations within such an additional period; or
(iii) after the expiration of any additional period of time indicated by the seller in accordance with paragraph (2) of article 48, or after the buyer has declared that he will not accept performance.