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The Litmaps Database
The Litmaps database is sourced from Semantic Scholar, Crossref, and OpenAlex. It consists of 270+ million articles.
Litmaps uses only articles that have Open Access Metadata. Article data is not altered by Litmaps, and appears as it does from our source providers.
The list of datasets in Litmaps include:
See a list of covered publishers here.
What is Open Access Metadata?
The Metadata of an article consists of all the information about that article, except for the actual paper contents. The metadata of an article includes:
Title
Publication date
Abstract
References
Citations
Open Access means that the publisher has made this information publicly accessible. We're legally only able to index Open Access Metadata, so we can't represent articles (or citations/references of articles) that don't have this supplied.
The Litmaps database uses all articles with available Open Access Metadata to search on and generate suggestions, to ensure the best coverage for your search.
Open Access (OA) articles are not the same as those with Open Access Metadata. OA articles are a subset of literature whose actual paper contents are publicly accessible. Litmaps contains both OA articles and closed-access articles, which are only accessible through publisher access (often through your institution).
Why is an article missing?
There are several reasons an article can be missing from the Litmaps database. Most often, the article doesn't have Open Access Metadata and isn't indexed by our source data providers.
Missing articles stem from the same issues that cause missing citations or references. Read the next section to learn more.
Why is an article missing citations or references?
Sometimes articles in Litmaps display a lower number of references and/or citations than an article is expected to have. This can be for several reasons:
You're comparing the citations and references to other sites (i.e. Google Scholar) which calculate them differently.
Those references/citations don't have Open Access Metadata.
Some newer articles may have a delay in their citations and references appearing.
Citations of older articles by very recent articles may similarly have a delay before appearing.
You're looking for a different version of the article, and the article you found in Litmaps is a different version of the article which has poor citation information.
What’s the coverage of the Litmaps database?
The Litmaps database includes 270+ million articles across a range of disciplines.
Since the Litmaps database largely pulls on Semantic Scholar, we can use their coverage as an indicator of the Litmaps database coverage.
A 2022 study published in Scientometrics compared the coverage of 56 scientific databases, and found Semantic Scholar has the second best relative subject coverage (Gusenbauer, 2022). The Litmaps database thus has a similarly high relative subject coverage, as well as additional data from OpenAlex and Crossref.
Why do I see duplicate articles in Litmaps?
Duplicate articles in Litmaps result from versioning issues and sourcing from our source data providers. They occur because articles may be listed with incorrect identifiers, or identical papers may be listed with different identifiers.
We run a deduplication process when ingesting data from our providers which resolves most duplicate articles. However, due to versioning issues, you may still find duplicate articles in Litmaps.
If you find duplicate articles, you can:
How does Litmaps handle article versioning?
Articles are often released in several versions: pre-print before release, followed by the formal publication, and often followed by ongoing revisions.
We've decided to only represent the most recent version of an article, when multiple are found. We'll also make sure to choose a version that has a minimum standard of metadata: some newer versions of articles get entered with missing fields, in which case we'd rather represent an older, higher-quality, version.
How does Litmaps handle poor quality articles?
Litmaps uses citations in the core search algorithm, but citations are vulnerable to biases stemming from citation hacking, predatory journals and otherwise not credible research. These issues manifest in all literature search tools, and are best addressed by improving the quality of data and providing transparent, user-controlled search methods.
To ensure the quality and reliability of all articles, the Litmaps database is updated weekly and the most recent, highest-cited version of each article is used in the application.
Litmaps is unique in offering several algorithms. You can change the search algorithm to search based on semantic similarity, instead of by connection.