cr_abstract             Get abstract
cr_agency               Check the DOI minting agency on one or more
                        dois
cr_citation_count       Get a citation count via CrossRef OpenURL
cr_cn                   Get citations in various formats from CrossRef.
cr_funders              Search the CrossRef Fundref API
cr_journals             Search CrossRef journals
cr_licenses             Search CrossRef licenses
cr_members              Search CrossRef members
cr_prefixes             Search CrossRef prefixes
cr_r                    Get a random set of DOI's through CrossRef.
cr_types                Search CrossRef types
cr_works                Search CrossRef works (articles)
filters                 Get filter details and names.
get_styles              Get list of styles from
                        github.com/citation-style-language/styles
id_converter            Get a PMID from a DOI, and vice versa.
rcrossref-defunct       Defunct functions in rcrossref
rcrossref-deprecated    Deprecated functions in rcrossref
rcrossref-package       rcrossref
