A numerical perspective on CrossRef.

In 2000, the world's leading scholarly publications formed an association to provide citation linking between peer-reviewed publications. It holds no full-text content, but rather offers online linking through digital object identifiers (DOIs). Using these numerical tags allows users to click from one citation to another. CrossRef gets around the open-access debate by linking only to citations. If users have access to those publications they can then access the article's full text. Nature Publishing Group (NPG) helped found CrossRef, and deposited CrossRef links to Nature in 2000. In 2001, NPG added 13 research and reviews journals, 28 specialist journals and several reference resources. Last month CrossRef released data showing how the network has grown and has been used.

1,657 is the number of publishers and societies participating in CrossRef.

65% is the proportion of non-profit publishers who have joined CrossRef.

1,066 is the number of libraries participating in CrossRef.

21,744,529 DOIs have been registered so far.

14,855 is the number of journals included in CrossRef.