Persistent identifiers (PIDs) are permanent references to a digital object (document, file, website, etc.), a person, or an organisation. PIDs make it easier to link and retrieve publications and research results and to link authors with their works. PIDs for digital objects (e.g. DOI) and for people (e.g. ORCID iD) even allow direct access to the digital objects or to information about the person via a resolver service.