How to format your references using the Challenges citation style

This is a short guide how to format citations and the bibliography in a manuscript for Challenges. For a complete guide how to prepare your manuscript refer to the journal's instructions to authors.

Using reference management software

Typically you don't format your citations and bibliography by hand. The easiest way is to use a reference manager:

PaperpileThe citation style is built in and you can choose it in Settings > Citation Style or Paperpile > Citation Style in Google Docs.
EndNoteFind the style here: output styles overview
Mendeley, Zotero, Papers, and othersThe style is either built in or you can download a CSL file that is supported by most references management programs.
BibTeXBibTeX syles are usually part of a LaTeX template. Check the instructions to authors if the publisher offers a LaTeX template for this journal.

Journal articles

Those examples are references to articles in scholarly journals and how they are supposed to appear in your bibliography.

Not all journals organize their published articles in volumes and issues, so these fields are optional. Some electronic journals do not provide a page range, but instead list an article identifier. In a case like this it's safe to use the article identifier instead of the page range.

A journal article with 1 author
Futuyma, D.J. Retrospective. Robert R. Sokal (1926-2012). Science 2012, 336, 816.
A journal article with 2 authors
Ozanne, S.E.; Hales, C.N. Lifespan: catch-up growth and obesity in male mice. Nature 2004, 427, 411–412.
A journal article with 3 authors
Babaev, E.; Sudbø, A.; Ashcroft, N.W. A superconductor to superfluid phase transition in liquid metallic hydrogen. Nature 2004, 431, 666–668.
A journal article with 4 or more authors
Gruene, P.; Rayner, D.M.; Redlich, B.; van der Meer, A.F.G.; Lyon, J.T.; Meijer, G.; Fielicke, A. Structures of neutral Au7, Au19, and Au20 clusters in the gas phase. Science 2008, 321, 674–676.

Books and book chapters

Here are examples of references for authored and edited books as well as book chapters.

An authored book
Quinquis, A. Digital Signal Processing using MATLAB®; ISTE: London, UK, 2008; ISBN 9780470610992.
An edited book
Chatterjee, S. Identity-Based Encryption; Sarkar, P., Ed.; Springer US: Boston, MA, 2011; ISBN 9781441993823.
A chapter in an edited book
Li, J.; Chen, J.; Wang, S. Dynamic Inventory Management with Short-Term Financing. In Risk Management of Supply and Cash Flows in Supply Chains; Chen, J., Wang, S., Eds.; International Series in Operations Research & Management Science; Springer: New York, NY, 2011; pp. 127–148 ISBN 9781461405108.

Web sites

Sometimes references to web sites should appear directly in the text rather than in the bibliography. Refer to the Instructions to authors for Challenges.

Blog post
Andrew, D. Why WHO Needs A Radical Rethink Of Its Draconian Approach To Cannabis Available online: (accessed on Oct 30, 2018).


This example shows the general structure used for government reports, technical reports, and scientific reports. If you can't locate the report number then it might be better to cite the report as a book. For reports it is usually not individual people that are credited as authors, but a governmental department or agency like "U. S. Food and Drug Administration" or "National Cancer Institute".

Government report
Government Accountability Office Surface Transportation: Restructured Federal Approach Needed for More Focused, Performance-Based, and Sustainable Programs; U.S. Government Printing Office: Washington, DC, 2008;

Theses and dissertations

Theses including Ph.D. dissertations, Master's theses or Bachelor theses follow the basic format outlined below.

Doctoral dissertation
Farooq, A.S. Singing the blues: Indicators of mental illness among nursing home elderly. Doctoral dissertation, California State University, Long Beach: Long Beach, CA, 2012.

News paper articles

Unlike scholarly journals, news papers do not usually have a volume and issue number. Instead, the full date and page number is required for a correct reference.

New York Times article
Feeney, K. A Focus on Cheese. New York Times 2011, NJ10.

In-text citations

References should be cited in the text by sequential numbers in square brackets:

This sentence cites one reference [1].
This sentence cites two references [1,2].
This sentence cites four references [1–4].

About the journal

Full journal titleChallenges
ISSN (online)2078-1547

Other styles