@online{online.luacode,
  title = {luacode package},
  year = 2012,
  url = {https://mirror.kku.ac.th/CTAN/macros/luatex/latex/luacode/luacode.pdf},
  note = {visited on 2022-03-10}
}

@online{online.pgf,
  title = {pgf Package},
  url = {https://ctan.org/pkg/pgf?lang=en},
note = {visited on 2021-01-10}
}

@online{online.xkeyval,
  title = {xkeyval Package},
  url = {https://ctan.org/pkg/xkeyval},
  note = {visited on 2021-03-10}
}

@online{online.luamplib,
  title = {luamplib package},
  year = {2022},
  url = {https://mirror.kku.ac.th/CTAN/macros/luatex/generic/luamplib/luamplib.pdf},
  urldate = {2022-02-22}
}

@online{online.metapost,
  title = {MetaPost system},
  year = 2020,
  url = {https://www.tug.org/docs/metapost/mpman.pdf},
  urldate = {2022-02-22}
}

@online{article.hobby,
title   = {Drawing Graphs with MetaPost},
 author = {John D. Hobby},
  url = {https://tug.org/docs/metapost/mpgraph.pdf}
}