diff --git a/README.md b/README.md
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+++ b/README.md
@@ -21,7 +21,7 @@ Some programs are in Jupyter (`.ipynb`) notebooks, some in `.py` files. For each
 
 |Run|Year|Programming Examples|
 |---|----|---|
-| [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Advent-2020.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FAdvent-2020.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FAdvent-2020.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Advent-2020.ipynb) | 2018 | <b><a href="ipynb/Advent-2020.ipynb" title="Puzzle site with a coding puzzle each day for Advent 2018 ">Advent of Code 2020</a></b> |
+| [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Advent-2020.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FAdvent-2020.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FAdvent-2020.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Advent-2020.ipynb) | <u>2020</u> | <b><a href="ipynb/Advent-2020.ipynb" title="Puzzle site with a coding puzzle each day for Advent 2018 ">Advent of Code 2020</a></b> |
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Advent-2018.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FAdvent-2018.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FAdvent-2018.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Advent-2018.ipynb) | 2018 | <b><a href="ipynb/Advent-2018.ipynb" title="Puzzle site with a coding puzzle each day for Advent 2018 ">Advent of Code 2018</a></b> |
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Advent%202017.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FAdvent%202017.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FAdvent%202017.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Advent%202017.ipynb) | 2017 | <b><a href="ipynb/Advent%202017.ipynb" title="Puzzle site with a coding puzzle each day for Advent 2017">Advent of Code 2017</a></b> |
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Advent%20of%20Code.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FAdvent%20of%20Code.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FAdvent%20of%20Code.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Advent%20of%20Code.ipynb) | 2016 | <b><a href="ipynb/Advent%20of%20Code.ipynb" title="Puzzle site with a coding puzzle each day for Advent 2016*">Advent of Code 2016</a></b> |
@@ -56,7 +56,7 @@ Some programs are in Jupyter (`.ipynb`) notebooks, some in `.py` files. For each
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/flipping.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2Fflipping.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2Fflipping.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/flipping.ipynb) | <u>2020</u> | <b><a href="ipynb/flipping.ipynb" title="Can you go through a deck of cards, guessing higher or lower correctly for each card?">Flipping Cards; A Guessing Game</a></b> |
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/RiddlerLottery.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FRiddlerLottery.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FRiddlerLottery.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/RiddlerLottery.ipynb) | 2019 | <b><a href="ipynb/RiddlerLottery.ipynb" title="Can you find what lottery number tickets these five friends picked?">Lottery</a></b> |
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/NightKing.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FNightKing.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FNightKing.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/NightKing.ipynb) | 2019 | <b><a href="ipynb/NightKing.ipynb" title="A battle between the army of the dead and the army of the living">How Many Soldiers to Beat the Night King?</a></b> |
-| [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Mean%20Misanthrope%20Density.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FMean%20Misanthrope%20Density.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FMean%20Misanthrope%20Density.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Mean%20Misanthrope%20Density.ipynb) | 2017 | <b><a href="ipynb/Mean%20Misanthrope%20Density.ipynb" title="How crowded will this neighborhood be, if nobody wants to live next door to anyone else?">The Misanthropic Neighbors</a></b> |
+| [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Mean%20Misanthrope%20Density.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FMean%20Misanthrope%20Density.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FMean%20Misanthrope%20Density.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Mean%20Misanthrope%20Density.ipynb) | 2017 | <b><a href="ipynb/Mean%20Misanthrope%20Density.ipynb" title="How crowded will this neighborhood be, if nobody wants to live next door to anyone else?">Misanthropic Neighbors</a></b> |
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Orderable%20Cards.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FOrderable%20Cards.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FOrderable%20Cards.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Orderable%20Cards.ipynb) | 2018 | <b><a href="ipynb/Orderable%20Cards.ipynb" title="Can you get your hand of cards into a nice order with just one move?">Properly Ordered Card Hands</a></b> |
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/TourDe538.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FTourDe538.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FTourDe538.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/TourDe538.ipynb) | <u>2020</u> | <b><a href="ipynb/TourDe538.ipynb" title="Solve a puzzle involving the best pace for a bicycle race.">Tour de 538</a></b> |
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/TwelveBalls.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FTwelveBalls.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FTwelveBalls.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/TwelveBalls.ipynb) | <u>2020</u> | <b><a href="ipynb/TwelveBalls.ipynb" title="A puzzle where you are given some billiard balls and a balance scale, and asked to find the one ball that is heavier or lighter, in a limited number of weighings">Weighing Twelve Balls</a></b> |