https://richardli.r-universe.dev/surveyPrevhttps://richardli.r-universe.dev/api/packages/surveyPrevhttps://richardli.r-universe.dev/surveyPrev/surveyPrev.pdfhttps://richardli.r-universe.dev/surveyPrev/doc/manual.htmlhttps://richardli.r-universe.dev/surveyPrev/NEWShttps://richardli.r-universe.dev/surveyPrev/NEWS.txthttps://richardli.r-universe.dev/surveyPrev/citationhttps://richardli.r-universe.dev/surveyPrev/citation.txthttps://richardli.r-universe.dev/surveyPrev/citation.cffhttps://richardli.r-universe.dev/surveyPrev/doc/vignette-data-preparation.html.asishttps://richardli.r-universe.dev/articles/surveyPrev/vignette-data-preparation.htmlhttps://richardli.r-universe.dev/surveyPrev/doc/vignette-main.html.asishttps://richardli.r-universe.dev/articles/surveyPrev/vignette-main.html