Call for Invitation for Proposal for the provision of Depurated and Delivered: Feasibility Study of Clean Mussels and Oysters. This invitation is for the provision of non-commercial services under the FAO rules that govern Letters of Agreement (hereinafter refered to as “Agreement” or “LoA”). Under these rules only non-profit, intergovernmental, and governmental organisations are eligible to sign LoAs with FAO.