Gray Literature in Engineering

WHAT IS A PREPRINT MANUSCRIPT?

Preprints are unpublished drafts of research papers posted online prior to formal peer review and journal publication. They allow researchers to share new findings faster, but they lack the rigorous vetting of published papers. Posting an Open Access (available free to the public) preprint speeds the dissemination of the work. Preprints are hosted on subject-specific preprint repositories like arXiv and chemRxiv.

Think of preprints as an early sneak peek at unvetted research.

Although preprints have not undergone the peer review process, they are of value to students conducting research and the scientific community.

PROS & CONS OF USING PREPRINTS

Pros:

• Access cutting-edge research: Preprints allow students to engage with the latest research findings in their field that have not yet gone through formal publication. This provides an opportunity to stay current.
• Show depth of research: Including relevant preprints in citations and bibliographies demonstrates a student's ability to find and utilize the most recent advancements, even if the research is not yet peer reviewed.
• Establish timelines: Citing preprints allows students to establish when certain discoveries were made public.

Cons:

• Unvetted research: Since preprints have not been peer reviewed, the research may contain errors, inaccurate interpretations, or even questionable results that could be misleading.
• Volatile content: Preprints may be edited or revised significantly prior to formal publication. What a student cites may change.
• Questionable credibility: Faculty may view preprints as having less credibility than peer-reviewed sources, especially in conservative disciplines. Students should follow guidelines.
• Difficult to assess quality: Without the vetting of peer review, it can be difficult for students to judge the validity and soundness of preprint studies and findings.

CITING A PREPRINT IN IEEE

A common citation style in engineering is IEEE. The IEEE template for citing a preprint includes the following: 

Author(s),   "Title."  Repository name,  Date uploaded.  Accessed Date. Available: url 

An example citation: 

N. J. Majaj and D. G. Pelli, “Deep learning: Using machine learning to study biological vision.” bioarXiv, Aug. 2017. Accessed Feb. 26, 2024. Available: https://doi.org/10.1101/178152

CITING AN ARXIV PREPRINT IN IEEE

IEEE style has a specific, simplified template for citing from arXiv: 

Author(s),   "Title,"  Year,  arXiv number.

An example citation: 

A. M. Dillamore, V. Belokurov, and N. W. Evans, “Radial halo substructure in harmony with the Galactic bar,” 2024, arXiv:2402.14907.

See our Research Guide on Citing with IEEE for more information.

Preprints have been included in Scopus since early 2021. Coverage includes preprints posted from 2017 onwards.
The repositories indexed are:

To find preprints in Scopus, after running a search, select “Preprints,” which exists as a top-level category on the results page, between Documents and Patents. Citation metrics are not tracked for preprints, so they can be sorted only by “Date (newest)” and “Relevance”.

Preprint results in Scopus also have fewer filtering options than typical Document search results, with no Subject Area, Keyword, or Funding Sponsor options. Instead there is a filter for “Repository,” allowing users to limit to arXiv (or other repositories) if desired. The same limiting behavior can be accomplished in the Scopus Advanced Query by using:

LIMIT-TO ( EXACTSRCTITLE , "Arxiv" )

In early 2023, the Preprint Citation Index was added to the suite of available database options in Clarivate’s Web of Science. The preprint repositories included are arXiv, bioRxiv, medRxiv, chemRxiv, and Preprints.org, with coverage dating back to the establishment of each repository.

These repositories can be searched inside Web of Science by choosing either “Preprint Citation Index” or the “All Databases” from the dropdown menu on the landing page:

Preprints are excluded by default in the "All Databases" option. To include preprints in search results, reject the “NOT Database: Preprint Citation Index” button after running a search:

Once this default is toggled off and the preprints are included in the main search, the Preprint Citation Index will appear in the Database filter and can be included or excluded as needed. Individual repositories can also be included or excluded using the “Repositories” filter.

Metrics are tracked for preprints in Web of Science, with citations and a citation alert available for each preprint. Filters are robust, including WoS Categories, Funding Agencies, and Grant Number. These options appear whether using the “All Databases” option or the “Preprint Citation Index.”

Inspec and Compendex are individual engineering databases hosted on the Engineering Village platform. They treat preprints slightly differently, and they can be searched independently or in combination on the EV platform.

INSPEC

Inspec began indexing preprints in 2016, and their coverage extends at least as far back as the year 2000. Preprints indexed in Inspec come from arXiv only. If searching only Inspec inside Engineering Village, keep this in mind. Inspec has a clear label [arXiv] on all their preprints, which looks like:

Preprints are included in search results by default.

COMPENDEX

Preprints indexed in Compendex currently come from arXiv, Research Square, IEEE's TechRxiv, and the “Applied Sciences” and “Physical Sciences” collections from inside the Social Science Research Network [SSRN]. Coverage includes preprints posted from 2017 onwards. 

Compendex also includes preprints by default in search results. They can be excluded by using the Document Type filter dropdown before or after running a search. To search only preprints from the beginning, the “pp” designator can be used with “DT” document type in Expert Search:

(“solar energy" wn TI) AND (pp wn DT)

wn = within
TI = title
pp = preprint
DT = document type

The Engineering Village platform allows limiting by 62 different physical properties (such as bit rate, luminance, and surface tension), and this unique feature can also be applied to preprint searches. Individual repositories can be included or excluded using either the Source Title or Repository filter. 

Preprints in Digital Science’s Dimensions Analytics come from arXiv, bioRxiv, ChemRxiv, EartharXiv, medArxiv, OSF Preprints, and 50 other preprint repositories from around the world. Dimensions indexes more preprint repositories by an order of magnitude than any other subscription database. Preprint indexing has been included in Dimensions since at least 2019, and coverage includes preprints posted from 2015 onwards.

In Dimensions, limiting to preprints is possible by using the Publication Type filter and selecting Preprint:

Individual repositories can be selected or omitted by using the Source Title filter.

Dimensions features a dynamic landing page, with a feed of recent documents ingested into the platform instead of only a search box. This means that from the landing page, a user can select Publication Type > Preprint and see all currently-indexed preprints, which allows comprehensive analysis and visualization of preprints as a whole.

This is a timeline tracking the total international preprint publication number from 2010 to 2023:

Citation metrics and Altmetrics are tracked for preprints within Dimensions, and sorting of results is available by Relative Citation Ratios (RCR) and Field Citation Ratios (FCR).