Crossmark - Crossref
The Crossmark button gives readers quick and easy access to the current status of an item of content, including any corrections, retractions, or updates to that record. Crossmark provides a cross-platform way for readers to quickly discover the status of a research output along with additional metadata related to the editorial process. Crucially, the Crossmark button can also be embedded in PDFs, which means that members have a way of alerting readers to changes months or even years after it’s been downloaded.

SemRepo.org
SemRepo is a large-scale RDF knowledge graph of GitHub repositories linked to scientific research. SemRepo captures fine-grained repository-level metadata (e.g., contributors, issues, programming languages) and interlinks this with external scholarly knowledge graphs: repositories to publications in LPWC, repository authors to their profiles in SemOpenAlex, and research artifacts (e.g., datasets, experiments) are linked via MLSea.