The UNESCO Chair Water, Ports and Historic Cities started the Blue Papers journal at SOAP | Stichting OpenAccess platforms. SOAP provides a dedicated Open Journal Systems installation, it applied for the ISSNs for Blue Papers, and it provided a Crossref sponsored membership for the UNESCO Chair.
As of February 2023 SOAP will sponsor Docomomo International as Crossref member. Docomomo International has still the same obligations and benefits as any other member, the prefix it used remains the same, but they have now SOAP representing them for Crossref services and it doesn’t pay fees to Crossref directly.