Every entity in OpenCitations Meta (https://opencitations.net/meta) is assigned persistent internal identifier called OpenCitations Meta Identifier (OMID). The OMID has structure [[entity_type_abbreviation]]/[[supplier_prefix]][[sequential_number]]. For example, the first journal article ever processed has OMID br/0601 (the full URI is https://w3id.org/oc/meta/br/0601), where br is the abbreviation of bibliographic resource, and 060 corresponds to the supplier prefix, helpful in recognising at a glance the index it belongs to (i.e., OpenCitations Meta). Finally, 1 indicates that this is the index's first bibliographic resource ever minted.