Zotero

Zotero is a free-of-charge tool for search and reference management, which helps in the finding, organising, citing and sharing of research results. It has a browser extension. The scope of function includes the fact that Zotero is now collaborating with the Retraction Watch database and warns you when you quote something that has been retracted. Furthermore, the detection of full texts from citations has been supplemented by Unpaywall.