d. The certificates shall be conspicuously displayed either in the cabin of the vehicle or one of the sides of the containers in accordance with the provisions of item 6 paragraph (d) above. e. Road vehicles and containers shall be sent annually to the appropriate authorities for purposes of inspection and renewal of the agreement. f. The agreement shall become invalidated if the essential characteristics of the road vehicle or container be modified or if there be a change of ownership. 13. I.S.R.T. ECOWAS LICENCE PLATES: Road vehicles and containers used by the transit transportation must carry ISRT-ECOWAS Licence Plates front and back and only when they are carrying transit goods. These Licence Plates shall be circular and 25 cm in diameter. The abbreviations ECOWAS-ISRT/CEDEAI TRIE shall be inscribed in capital roman letters. These letters will be a little under 10 cm high and the stroll 2 cm thick. These licence plates shall be reflective blue in colour and all letters shall be reflective white and patterned after the following model: Echelle 1/5