https://r-lib.r-universe.dev/xopenhttps://r-lib.r-universe.dev/api/packages/xopenhttps://r-lib.r-universe.dev/xopen/xopen.pdfhttps://r-lib.r-universe.dev/xopen/doc/manual.htmlhttps://r-lib.r-universe.dev/xopen/NEWShttps://r-lib.r-universe.dev/xopen/NEWS.txthttps://r-lib.r-universe.dev/xopen/citationhttps://r-lib.r-universe.dev/xopen/citation.txthttps://r-lib.r-universe.dev/xopen/citation.cff