[Letter by the President Transmitting a Letter dated 6 December 2018, from H.E. Amal Mudallali, Permanent Representative of Lebanon and H.E. Francisco Duarte Lopes, Permanent Representative of Portugal, Co-chairs of the Ad hoc Open-ended Working Group to Consider Options to Address possible Gaps in International Environmental law and Environmental related Instruments, inviting Member States to the First Substantive Session of the Ad hoc Open-ended Working Group o be held from Monday, 14 January to Friday, 18 January 2019 at the United Nations Office in Nairobi]