https://c16267.r-universe.dev/ppmSDRhttps://c16267.r-universe.dev/api/packages/ppmSDRhttps://c16267.r-universe.dev/ppmSDR/ppmSDR.pdfhttps://c16267.r-universe.dev/ppmSDR/doc/manual.htmlhttps://c16267.r-universe.dev/ppmSDR/citationhttps://c16267.r-universe.dev/ppmSDR/citation.txthttps://c16267.r-universe.dev/ppmSDR/citation.cffhttps://c16267.r-universe.dev/ppmSDR/doc/ppmSDR.Rmdhttps://c16267.r-universe.dev/articles/ppmSDR/ppmSDR.pdf