Sort Cite with Year It was written

sortR.awk

BEGIN{
  Count=0
}
{
  input[Count]=$0
  Count++;
}
function SortByYear(i1, v1, i2, v2, l, r) {
    Year1=match(v1, /20([0-9]){2}/, year)
    v1=year[0]
    Year2=match(v2, /20([0-9]){2}/, year)
    v2=year[0]
    return int(v1)-int(v2)
}
END{
  asort(input, out, "SortByYear")
  for (i in out) {
      print out[i]
  }
}