Within an amsart document, you can add a bibliography without a BibTeX file, by directly use the \bibitem command inside a begin{thebibliography} clause. See e.g., here.
Had I used BibTeX, I could also use the bibliographystyle{alpha} to change the style. This does not work in the direct citation format using bibitem. Is there a way to enforce a style on the first option?
Also related , but was asked over 5 years ago without a direct solutions.
\bibitemis simply you decided on the formatting yourself, that's rather the point – Joseph Wright Aug 13 '20 at 18:51thebibliographyenvironment for you in a style as specified by the bibstyle. If you choose to write the items yourself, then you have full control over the style. – David Carlisle Aug 13 '20 at 18:56[AS00]for a reference instead of[3])? – Amir Sagiv Aug 13 '20 at 19:48\bibitem[zzzwibble]{zzz} any text for this reference– David Carlisle Aug 13 '20 at 19:51thebibliographyenvironments by hand for each and every one of your papers. – Mico Aug 14 '20 at 04:51