https://rpkgs.r-universe.dev/gg.layershttps://rpkgs.r-universe.dev/api/packages/gg.layershttps://rpkgs.r-universe.dev/gg.layers/gg.layers.pdfhttps://rpkgs.r-universe.dev/gg.layers/doc/manual.htmlhttps://rpkgs.r-universe.dev/gg.layers/NEWShttps://rpkgs.r-universe.dev/gg.layers/NEWS.txthttps://rpkgs.r-universe.dev/gg.layers/citationhttps://rpkgs.r-universe.dev/gg.layers/citation.txthttps://rpkgs.r-universe.dev/gg.layers/citation.cff