@manual{GNULib,
  title =        "{The GNU Portability Library}",
  organization = "{Free Software Foundation}",
  bibdate =      "February 24, 2019",
  bibsource =    "https://www.gnu.org/software/gnulib/manual"
}

@manual{GNUCLib,
  title =        "{The GNU C Library}",
  organization = "{Free Software Foundation}",
  bibdate =      "February 1, 2020",
  bibsource =    "https://www.gnu.org/software/libc/manual"
}