Mendeley and Elsevier Donation for 2016

For their third straight year, Mendeley and Elsevier have kindly supported the open source Citation Style Language project with a $5000 donation. Donations allow us to hire developers for small projects, purchase materials such as the latest style manuals, and support our style repository maintainers. We’re very grateful for this continuing sponsorship!

In July, Carles Pina from Mendeley also updated over 150 CSL styles for Elsevier journals. Our collection now counts over 8300 free CSL styles, for use with Mendeley, Zotero, Papers, and many other applications.

Further development of the Citation Style Language specification has been on the back burner as we have focused on maintaining the CSL style repository. Fortunately, previous donations allowed us to pay a bounty to Sylvester Keil for the development of an automated system to check GitHub pull requests. The system, coined “Sheldon” after the socially inept and obsessive-compulsive character Sheldon Cooper from The Big Bang Theory, has become a great time-saver and helped us improve the quality of our styles. This focus on quality seems to be paying off: a recent study [paywalled] in The Journal of Academic Librarianship concluded that Zotero and Mendeley, using CSL styles, produced the most accurate citations among leading reference managers.

Going forward, we keep trying to handle all style repository contributions in a timely manner. We also plan to return to development of the Citation Style Language specification in the coming year.

We’d like to end with a call to other publishers. Please do reach out if you want to make sure we have accurate and up-to-date CSL styles for all your journals. Often, all we need is a spreadsheet of your journal metadata, with journal titles, ISSNs, and, if multiple citation formats are used across your collection, an indication of which journal uses which citation format. We’ll gladly (and without charge) use this metadata to generate CSL styles for all your journals. You can also help us by standardizing citation formats across your journals.

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Mendeley and Elsevier Donation for 2015

For a second year, Mendeley and Elsevier have generously supported the CSL project with a $5,000 donation. Donations like these allow us to dedicate time to the project, cover expenses, and pay out bounties for third-party work—in short, they help to keep CSL thriving. Our heartfelt thanks!

Over the past few months, Sankar Murugesan from Elsevier has also been contributing many custom CSL styles for Elsevier journals that don’t (yet) use one of the standard Elsevier citation formats. In addition, we were happy to see that Mendeley Desktop now recognizes the locale of non-English CSL styles, while providing an easy way to use CSL styles in other languages (see our guest post on the Mendeley blog).

In Related News

We recently created a CSL style formatter as part of our efforts to make it easier to contribute styles. We contributed code to Zotero, which now like Mendeley allows users to quickly change the language used with their CSL styles (see the Zotero blog post). As the CSL project has become ever more mature and popular, we created a governance document to make our structure and decision-making more transparent to outsiders. Finally, part of this year’s donations have been reserved to pay a bounty to Sylvester Keil, who is developing a system to provide better feedback to style contributors. We are also looking for a new maintainer/developer of the Visual CSL Editor. Thanks to the donations made to the CSL project, we are able to offer (limited) funding to anybody willing to take over this work from Steve Ridout, the editor’s original developer.

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Papers and Springer Donation

Today, with 30 software products using the Citation Style Language (CSL), and a style repository with over 7700 styles, we are excited to announce that Papers and Springer have made a $5000 donation to CSL.

Our collaboration with Papers started in 2011, when Papers2 for Mac shipped with CSL-based citation features. Papers’ largest contribution to CSL came from former Papers-programmer Charles Parnot, who created a system to automatically generate CSL styles for journals with the same citation style. He used this setup to contribute over 1300 CSL styles for Springer journals, and today, over 6000 of our journal-specific CSL styles have been automatically generated. Papers also introduced the long-running and still ongoing “A Serial for a Style” program, rewarding contributors of CSL styles with free Papers licenses.

We are thankful for the appreciation and support shown through this donation. As before, funds available to the CSL project will be used to support the style repository maintainers and CSL developers, and to finance the creation of new tools. Last year, this resulted in a more user-friendly CSL validator. We migrated our in-depth documentation (including the CSL primer and specification) to a new platform that is both mobile-friendly and easier to maintain. We also improved Zotero’s built-in CSL editor.

This year, we plan to further streamline our style submission process. Submissions on GitHub are already automatically checked, but the resulting error reports are difficult to interpret. By offering a bounty, we were able to find a professional programmer who just started work to translate these automated reports into easy-to-understand feedback, and provide contributors with detailed instructions on how to correct their submissions. And last but not least, we also hope to pick up the pace again on creating the next version of CSL.

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Mendeley Donates to the CSL Project

CSL has seen a lot of growth in recent years: more than 20 software products use CSL (see the frontpage), and we offer over 6750 free citation styles, covering thousands of scientific journals.

We could only have come this far with our great user community, and with a lot of institutional support from Mendeley, Papers, Zotero, and others.

Mendeley has been using CSL since their first release in 2008, and adopted Frank Bennett’s citeproc-js CSL processor in 2010. They have since moved away from simply using CSL to become one of our biggest contributors. Carles Pina of Mendeley helped us improve the central CSL style repository, and create CSL styles for 1500 Elsevier journals. Mendeley also collaborated with Columbia University Libraries to created the Visual CSL Editor, which was funded by a Sloan Foundation Award and released in 2012.

Now, Mendeley, together with Elsevier, stepped up once more, and made the first major financial contribution to the CSL project. We received a $5000 donation, which we will use to cover project expenses and help ensure the long-term sustainability of CSL. Mendeley is one of the most popular products to use CSL, and this level of involvement is crucial in helping us move CSL forward. We hope others will follow Mendeley’s lead, and we look forward to continue improving CSL.

In particular, we will collaborate with Zotero on their upcoming data model redesign, which should help us provide guidance to other projects on which fields each item type should carry and, among other things, improve support for primary and archival sources. We also plan to adopt features from Frank Bennett’s Multilingual Zotero into official CSL, such as better support for legal citations and citing items in multiple languages. We’ll of course continue to maintain the project website and documentation, and handle style submissions to the repository. Finally, we’ll keep reaching out to publishers to further increase the number of journals covered by CSL styles.

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Citation Style Language 1.0.1 Update

The Citation Style Language (CSL) team is happy to announce CSL 1.0.1.

CSL 1.0.1 is an (almost completely) backwards compatible release, and CSL 1.0 styles and locale files don’t have to be updated to work with CSL 1.0.1-compatible software. CSL 1.0.1 is a relatively minor update, but adds a variety of new features to CSL, and an extra layer of polish to both the specification and schema. The CSL 1.0.1 specification is accompanied by CSL 1.0.1 release notes, which give a comprehensive overview of the changes in this update.

State of the Union

This is the first update of the CSL schema since the release of CSL 1.0 in 2010. While CSL development has slowed since the flurry of activity leading up to the release of 1.0, we consider the project to be in great shape. CSL 1.0 has proven to be a very popular release, and we now have a well-curated collection of over 2500 CSL 1.0 styles, many of which have been contributed by users. All styles are now available under the permissive Creative Commons Attribution-ShareAlike license. A redesign of the Zotero Style Repository page has made browsing and searching styles easier. CSL 1.0 is now supported by Zotero, Mendeley, Papers, and Qiqqa, and we expect that these programs will support CSL 1.0.1 in the near future.

In addition to Frank Bennett’s citeproc-js, used by Zotero, Mendeley, and Qiqqa, there are several other actively maintained open source CSL processors. The PHP-based citeproc-php by Ron Jerome offers CSL support in Drupal through the Bibliography Module. The Haskell-based citeproc-hs by Andrea Rossato adds CSL support to the versatile Pandoc document converter. Finally, the Ruby-based citeproc-ruby, by Sylvester Keil, can easily be deployed for the web, and has recently been accepted as a 2012 Google Summer of Code project .

A collaboration between Columbia University Libraries and Mendeley is underway to create a more user-friendly CSL editor (although this previously has proven to be quite the challenge). Another exciting development is the work of Frank Bennett on his forks of Zotero and CSL to revolutionize the field of multilingual and legal citation management, the progress of which can be followed on his website

Posted in CSL Releases, News

CSL 1.0 First Anniversary

It’s been a year since version 1.0 of the Citation Style Language was released, but now is as an exciting time as ever. Zotero 2.1, Mendeley 0.9.8 and Papers2 now all use CSL 1.0 for citation formatting (Zotero and Mendeley both use citeproc-js, the open source JavaScript CSL 1.0 processor by Frank G. Bennett, Jr.). The document converter Pandoc now supports citeproc-hs 0.3.2, an open source Haskell CSL 1.0 processor, and work is ongoing for CSL 1.0 processors written in PHP ( and Ruby ( Finally, Zotero developers created citeproc-node, a NodeJS wrapper for citeproc-js, for easy server-side deployment.

With so many parties on board, the main challenge for the next few months will be the creation of a CSL 1.0 style repository, similar to the existing Zotero Style Repository for CSL 0.8.1 styles. Preferably, this repository should use a decentralized version control system like Git to handle the distribution and contribution of CSL styles, and have a front end for users to browse, preview and install styles. Interested parties are strongly invited to participate in the xbiblio mailing list to discuss and help out with these future improvements.

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CSL 1.0 Specification Update 2010-05-30


The CSL 1.0 specification update of 2010-05-30 includes the following changes:

  • clarified behavior of the line-spacing and entry-spacing attributes [diff]
  • clarified behavior of the position condition when used for bibliography formatting [diff]
  • clarified behavior of the et-al-subsequent attributes [diff]
  • changed the handling of name suffixes (now aligns with Chicago Manual of Style) [diff]
  • changed et-al abbreviation to use a context-dependent prefix (aligns with CSL processor in Zotero 2.0) [diff]
  • clarified the behavior of the choose element, and mentioned the dual effect of the match attribute on if and else-if elements [diff]
  • removed the substitution of empty date variables by the “no date” term [diff]

Discussions on these changes can typically be found at the xbiblio mailing list.

A Note on CSL Versioning

A three-number system (e.g. “1.2.3”) will be used for versioning of the CSL schema and specification. The first and second number are used for respectively major and minor backwards incompatible updates to the CSL schema (these updates will require upgrading of existing CSL styles). The third number is used for small backwards compatible updates. Each update to the CSL schema will be accompanied by an updated CSL specification. In addition, minor date-versioned updates to the CSL specification can be released without accompanying changes to the CSL schema (as is the case for the current specification update).

Posted in CSL Releases, News

Citation Style Language 1.0

The Citation Style Language (CSL) team is proud to announce CSL 1.0, a free and open XML language for the formatting of citations and bibliographies.

A New Home is the new home of the CSL project, hosting the schema, documentation, project news, and more. In the near future will also host the style repository currently found at

By Academics, for Academics

CSL 1.0 has been developed by academics, for academics. The members of the development team hail from diverse fields, covering social science, law, and natural science. We are keenly aware of the diverse and demanding requirements of scholars working in different languages and different fields of research. At the end of an intensive year of development work, we feel confident that CSL 1.0 marks an important step forward in academic productivity.

New features

The top 5 new features that we would like to highlight:

  • In-field markup: CSL 1.0 compatible programs now support markup within titles, with support for superscript, subscript, small capitals, italics and boldface.
  • Full localization: whereas CSL 0.8 only offered localization of terms, CSL 1.0 offers full style localization, adding support for localized dates and punctuation.
  • Names: many new features are related to names. Name disambiguation has been refined, and name particles (“van” in “Ludwig van Beethoven”) can now be sorted and rendered according to conventions that reflect the culture and personal preferences of each author.
  • Documentation: the schema for the 1.0 release is accompanied by a full set of documentation. A specification gives all the details on CSL 1.0, and upgrade notes discuss the changes made between CSL 0.8 and 1.0. A primer offers a concise tutorial on editing CSL 1.0 styles.
  • CSL processors: CSL 1.0 is released alongside citeproc-js, the first CSL 1.0 compatible CSL processor, as well as a CSL 1.0 test suite. Various features of CSL 1.0 and citeproc-js can be seen in action in the online demo. Adding support for CSL was never easier.

CSL 1.0 includes many more improvements. For a full overview, see the upgrade-notes.

Using Existing Styles

Zotero support for CSL 1.0 is scheduled for Zotero 2.1. When released, the Zotero team will upgrade the more than thousand CSL 0.8 styles hosted in the Zotero Style Repository. To upgrade a CSL 0.8 style yourself, follow the upgrade procedure.

Posted in CSL Releases, News