Add a source by identifier

When you know a paper's DOI, PMID, arXiv ID or ISBN, you do not need to search for it. Paste the identifier into the search box of Cite or the Find papers page, and Papero looks up that one record. A lookup is not a paper search, so it rarely counts toward your paper search allowance, and it still works when you have used your paper searches or reached the daily paper search limit.

What you can paste

The whole box must hold the identifier, in one of these forms:

• DOI: the DOI itself, such as 10.1038/nature14539, with doi: in front, or as a doi.org link.
• arXiv ID: with arXiv: in front, such as arXiv:1706.03762, or an arxiv.org link to the paper's abstract, PDF or HTML page. Old-style IDs such as arXiv:hep-th/9901001 work too.
• PMID: with PMID in front, such as PMID: 33657296, or a PubMed link.
• ISBN: with ISBN in front, or a 13-digit ISBN on its own. Hyphens and spaces are fine, and an ISBN-10 works with ISBN in front.

A number on its own, or words around an identifier, count as an ordinary search. In the Add a custom citation drawer, whose field only ever holds an identifier, a bare PMID, a bare new-style arXiv ID and a bare ISBN-10 work as well. See Custom citations.

Look up a source in Cite

1. Put your cursor where the citation goes and open Cite. See Cite as you write.
2. In the Search tab, paste the identifier.
3. Wait for the card, then press Cite.

A DOI or an ISBN is looked up as soon as you stop typing. A PMID or an arXiv ID is looked up when you paste it whole or press Enter, because each digit you type on the way makes another valid ID. Until then the hint under the box says, for example, Press Enter to look up this PMID.

On the Find papers page, the same lookup gives you one card to save with Save to library.

The Journal impact filter never hides a paper you looked up by its identifier. See Journal impact filter.

Paste a DOI into your text

You can also paste a DOI straight into your document. When the clipboard holds just one DOI (on its own, with doi:, or as a doi.org link), and you paste it at the cursor with no text selected, Cite opens on that paper instead of putting the DOI in your text. Press Cite to cite it. If you close Cite without citing it, Papero puts the DOI back in your text where you pasted it.

This does not happen inside a code block, where the DOI is pasted as text.

Where the details come from

• DOI: OpenAlex first. When OpenAlex does not know the DOI, doi.org, which hands over the record from Crossref or DataCite.
• arXiv ID: the DOI that arXiv registers with DataCite for the paper, through doi.org. OpenAlex adds the abstract, the citation count and whether it was retracted, when it knows the paper.
• PMID: OpenAlex.
• ISBN: Crossref's record for the whole book, then the book's DOI, looked up as above. A book that has no DOI at Crossref is not found this way.

The services get the identifier and Papero's contact email address, nothing about you. Check that each source says what your text claims it says.

When a lookup fails

The line under the box says what went wrong:

• That DOI doesn't look right. Check it, or add the source by hand. The identifier has the wrong shape, or an ISBN's check digit is wrong. The same line names an arXiv ID, PMID or ISBN.
• No paper found for that DOI. Check it, or add the source by hand. No record answered for it. A book without a DOI at Crossref ends here too.
• The DOI service is not answering. Add the source by hand. or The lookup service is not answering. Add the source by hand. You can try again later.

To add the source by hand, press Add custom citation at the bottom of Cite. You can paste the identifier there too and press Fetch details. See Custom citations.

Free tools on papero.ai

To turn identifiers into a reference list without opening a document, the free tools on papero.ai work without an account: DOI to citation, PMID to citation, ISBN to citation and arXiv to BibTeX.

Next: choose a citation style.