The Crossref Curriculum

References

Registering references means submitting them as part of your Crossref metadata deposit. It is optional, but strongly encouraged. Registering references is a prerequisite for participating in Cited-by.

Note that registering references is not the same as reference linking - learn more about the differences.

The benefits of registering references as part of your metadata include:

  • making your content more discoverable (especially if your references are open),
  • enabling evaluation of research, and
  • helping with citation counts.

Learn more about the Initiative for Open Citations (I4OC).

Whenever you register content with us, make sure you include your references in the submission.

Including references (or adding them to an existing deposit) can be done by:

On this page, learn more about:

Making your references open

All metadata that members register with us is publicly available (open) through our various metadata search and API services. However, references have historically been treated differently from all other metadata.

Our reference distribution policy means that members joining since 1 January 2018 have their references set to open by default, and are included in our full list of members who have opened their references for distribution.

Any member can choose to set their references to open, limited, or closed at any time. The policy can be set differently per DOI prefix.

We recommend that members use the open option, to support linking between research outputs. By doing this, they enable the community to determine how work has been received and developed, and how ideas have evolved over time. Learn more about reference distribution options, and look at any member’s Participation Report to see if their references are open.

Reference distribution options

If references are submitted to a prefix set to limited or closed, they do not appear in our public APIs, but are used to update citation counts and for citation lists returned by Cited-by. Limited references are visible in Crossref APIs, but only to Metadata Plus subscribers.

References setting Who can view references in Crossref APIs? Do works appear in citation lists from Cited-by?
Open Everyone Yes
Limited Metadata Plus users Yes
Closed No-one Yes
No deposit No-one No

If you joined us before January 2018 and want to make your references publicly available (this is recommended), please contact us and we’ll enable reference distribution for your prefix (or prefixes). To enable open references for individual items, you can include a reference_distribution_opt flag within your <journal_article> element, for example: <journal_article publication_type="full_text" reference_distribution_opts="any">

To check if you (or your service provider) are including references in your metadata deposits, you can:

To find out if your references are currently set to open, limited, or closed, you can:

If you need further help, please contact us.

How to deposit references for users of direct deposit of XML

When depositing references as part of your content registration XML, mark up individual citations according to our deposit schema section. For example:

<citation key="ref1">
  <journal_title>Current Opinion in Oncology</journal_title>
  <author>Chauncey</author>
 <volume>13</volume>
 <first_page>21</first_page>
 <cYear>2001</cYear>
</citation>

Marking up each element allows us to be very precise when identifying potential matches with registered DOIs.

If you know the DOIs of individual citations, include them. We’ll use the metadata deposited for the DOI when generating Cited-by matches:

<citation key="ref2">
<doi>10.5555/small_md_0001</doi>
</citation>

References may also be included as an unstructured citation. This option is not as precise as including an already-matched DOI or marking up a citation into individual elements.

<citation key="ref=3">
<unstructured_citation>Clow GD, McKay CP, Simmons Jr. GM, and Wharton RA, Jr. 1988. Climatological observations and predicted sublimation rates at Lake Hoare, Antarctica. Journal of Climate 1:715-728.</unstructured_citation>
</citation>

As well as for depositing conventional references, data and software citations can also be deposited by inserting them into an item’s references metadata. To do so, follow the general process for depositing references as described above. Members can deposit the full data or software citation as an unstructured reference, or they can employ any number of reference tags currently accepted by Crossref. It’s always best to include the DOI (either DataCite or Crossref) for the dataset if possible.

Current elements for citation tagging

  • <issn>: ISSN of a series (print or electronic)
  • <journal_title>
  • <author>: first author of an article or other publication
  • <volume>: volume number (journal or book set)
  • <issue>: journal issue
  • <first_page>
  • <cYear>: year of publication
  • <article_title>: journal article, conference paper, or book chapter title
  • <isbn>
  • <series_title>: title of a book or conference series
  • <volume_title>: book or conference proceeding title
  • <edition_number>
  • <article_title>
  • <std_designator>
  • <standards_body_name>
  • <standards_body_acronym>
  • <component_number>: the chapter, section, part number for a content item in a book
  • <unstructured_citation>: citations for which no structured data is available. Crossref’s ability to process unstructured citations is limited (learn more about querying with formatted citations)
  • <doi>: include the DOI wherever possible

Learn more about the <citation> element in the schema documentation.

All citation elements are optional, but please submit as much information as you can to help us match your citations to DOIs.

Journal citations should include either <issn> or <journal_title> or both. <journal_title> only is preferred over <issn> only. In addition the first author (<author>) and <first_page number> should be submitted. <first_page> number is preferred, but for those citations that are “in press”, the author should be submitted.

When submitting a book or conference citation, you should include an <isbn>, <series_title>, <volume_title>, or any combination of these three elements as may be available.

A citation for a standard must include a standard designator (<std_designator>) as well as the name and acronym of a standards body (<standards_body_name>, <standards_body_acronym>). These elements are required for identifying a citation of a standard.

Metadata deposit example

References may be included with a metadata deposit. The references are included within the <citation_list> element. Review the example below or download an XML file.

<doi_batch xmlns="http://0-www.crossref.org.libus.csd.mu.edu/schema/4.3.7" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="4.3.7" xsi:schemaLocation="http://0-www.crossref.org.libus.csd.mu.edu/schema/4.3.7 http://0-www.crossref.org.libus.csd.mu.edu/schema/deposit/crossref4.3.7.xsd">
 <head>
  <doi_batch_id>1dbb27d1030c6c9d9d-7ff0</doi_batch_id>
  <timestamp>200504260247</timestamp>
  <depositor>
   <depositor_name>your name</depositor_name>
   <email_address>your@email.com</email_address>
  </depositor>
  <registrant>WEB-FORM</registrant>
 </head>
 <body>
  <journal>
   <journal_metadata>
	<full_title>Test Publication</full_title>
	<abbrev_title>TP</abbrev_title>
	<issn media_type="print">12345678</issn>
   </journal_metadata>
   <journal_issue>
	<publication_date media_type="print">
 	<month>12</month>
 	<day>1</day>
 	<year>2005</year>
	</publication_date>
	<journal_volume>
 	<volume>12</volume>
	</journal_volume>
	<issue>1</issue>
   </journal_issue>
<!--This is the article's metadata-->
   <journal_article publication_type="full_text">
	<titles>
 	<title>Article 12292005 9:32</title>
	</titles>
	<contributors>
 	<person_name sequence="first" contributor_role="author">
  	<given_name>Bob</given_name>
  	<surname>Surname</surname>
  	<ORCID>http\://orcid.org/0000-0002-4011-3590</ORCID>
 	</person_name>
	</contributors>
	<publication_date media_type="print">
 	<month>12</month>
 	<day>1</day>
 	<year>2004</year>
	</publication_date>
	<pages>
 	<first_page>100</first_page>
 	<last_page>200</last_page>
	</pages>
	<doi_data>
 	<doi>10.50505/test_20051229930</doi>
 	<resource>http://0-www.crossref.org.libus.csd.mu.edu/</resource>
	</doi_data>
<!--the list of references cited in the above article-->
	<citation_list>
 	<citation key="ref1">
  	<journal_title>Current Opinion in Oncology</journal_title>
  	<author>Chauncey</author>
  	<volume>13</volume>
  	<first_page>21</first_page>
  	<cYear>2001</cYear>
 	</citation>
 	<citation key="ref2">
  	<doi>10.5555/small_md_0001</doi>
 	</citation>
 	<citation key="ref=3">
  	<unstructured_citation>Clow GD, McKay CP, Simmons Jr. GM, and Wharton RA, Jr. 1988. Climatological observations and predicted sublimation rates at Lake Hoare, Antarctica. Journal of Climate 1:715-728.</unstructured_citation>
 	</citation>
	</citation_list>
   </journal_article>
  </journal>
 </body>
</doi_batch>

Resource-only deposit example

References may be added to an existing metadata record using a resource-only deposit. Review the example below or download an XML file.

<doi_batch xmlns="http://0-www.crossref.org.libus.csd.mu.edu/doi_resources_schema/4.3.6" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="4.3.6" xsi:schemaLocation="http://0-www.crossref.org.libus.csd.mu.edu/doi_resources_schema/4.3.6 http://0-www.crossref.org.libus.csd.mu.edu/schema/deposit/doi_resources4.3.6.xsd">
 <head>
  <doi_batch_id>123456</doi_batch_id>
  <depositor>
   <depositor_name>your name</depositor_name>
   <email_address>support@crossref.org</email_address>
  </depositor>
 </head>
 <body>
  <doi_citations>
<!--The DOI of the article that contains the citations  -->
   <doi>10.5555/small_md_0001</doi>
<!--The list of references cited in the above article -->
   <citation_list>
	<citation key="ref1">
 	<journal_title>Current Opinion in Oncology</journal_title>
 	<author>Chauncey</author>
 	<volume>13</volume>
 	<first_page>21</first_page>
 	<cYear>2001</cYear>
	</citation>
	<citation key="ref2">
 	<doi>10.5555/small_md_0001</doi>
	</citation>
	<citation key="ref=3">
 	<unstructured_citation>Clow GD, McKay CP, Simmons Jr. GM, and Wharton RA, Jr. 1988. Climatological observations and predicted sublimation rates at Lake Hoare, Antarctica. Journal of Climate 1:715-728.</unstructured_citation>
	</citation>
   </citation_list>
  </doi_citations>
 </body>
</doi_batch>

Page owner: Laura J. Wilkinson   |   Last updated 2020-April-08