diff --git a/README.md b/README.md
index 6f7b796..399d491 100644
--- a/README.md
+++ b/README.md
@@ -8,10 +8,10 @@
 
 This project contains **pytudes**—Python programs, usually short, for perfecting particular programming skills.
 Some programs are in Jupyter (`.ipynb`) notebooks, some in `.py` files. For each notebook you can:
-- Click on [co](https://colab.research.google.com) to **run** the file on Colab
-- Click on [dn](https://deepnote.com) to **run** the notebook on DeepNote
-- Click on [my](https://mybinder.org) to **run** the notebook on MyBinder
-- Click on [nb](https://nbviewer.jupyter.org/) to **view** the notebook on NBViewer
+- Click on [c](https://colab.research.google.com) to **run** the file on Colab
+- Click on [d](https://deepnote.com) to **run** the notebook on DeepNote
+- Click on [m](https://mybinder.org) to **run** the notebook on MyBinder
+- Click on [n](https://nbviewer.jupyter.org/) to **view** the notebook on NBViewer
 - Click on the title to **view** the notebook on github.
 - Hover over the title to **view** a description.
 
@@ -39,7 +39,8 @@ Some programs are in Jupyter (`.ipynb`) notebooks, some in `.py` files. For each
 |Run|Year|Logic and Number Puzzles|
 |---|----|---|
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Cryptarithmetic.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FCryptarithmetic.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FCryptarithmetic.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Cryptarithmetic.ipynb) | 2014 | <b><a href="ipynb/Cryptarithmetic.ipynb" title="Substitute digits for letters and make NUM + BER = PLAY">Cryptarithmetic</a></b> |
-| [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Countdown.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FCountdown.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FCountdown.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Countdown.ipynb) | <u>2020</u> | <b><a href="ipynb/Countdown.ipynb" title="Solving the equation 10 _ 9 _ 8 _ 7 _ 6 _ 5 _ 4 _ 3 _ 2 _ 1 = 2016. From an Alex Bellos puzzle">Four 4s, Five 5s, and Countdown to 2016</a></b> |
+| [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Euler's%20Conjecture.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FEuler's%20Conjecture.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FEuler's%20Conjecture.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Euler's%20Conjecture.ipynb) | 2018 | <b><a href="ipynb/Euler's%20Conjecture.ipynb" title="Solving a 200-year-old puzzle by finding integers that satisfy a<sup>5</sup> + b<sup>5</sup> + c<sup>5</sup> + d<sup>5</sup> = e<sup>5</sup>">Euler's Sum of Powers Conjecture</a></b> |
+| [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Countdown.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FCountdown.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FCountdown.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Countdown.ipynb) | <u>2020</u> | <b><a href="ipynb/Countdown.ipynb" title="Solving the equation 10 _ 9 _ 8 _ 7 _ 6 _ 5 _ 4 _ 3 _ 2 _ 1 = 2016. From an Alex Bellos puzzle">Four 4s, Five 5s, and Countdowns</a></b> |
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Socks.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FSocks.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FSocks.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Socks.ipynb) | 2019 | <b><a href="ipynb/Socks.ipynb" title="What is the probability that you will be able to pair up socks as you randomly pull them out of the dryer?">Pairing Socks</a></b> |
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Sicherman%20Dice.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FSicherman%20Dice.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FSicherman%20Dice.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Sicherman%20Dice.ipynb) | 2018 | <b><a href="ipynb/Sicherman%20Dice.ipynb" title="Find a pair of dice that is like a regular pair of dice, only different">Sicherman Dice</a></b> |
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Golomb-Puzzle.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FGolomb-Puzzle.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FGolomb-Puzzle.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Golomb-Puzzle.ipynb) | 2014 | <b><a href="ipynb/Golomb-Puzzle.ipynb" title="A Puzzle involving placing rectangles of different sizes inside a square">Sol Golomb's Rectangle Puzzle</a></b> |
@@ -51,15 +52,15 @@ Some programs are in Jupyter (`.ipynb`) notebooks, some in `.py` files. For each
 |Run|Year|The Riddler (from 538)|
 |---|----|---|
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Riddler%20Battle%20Royale.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FRiddler%20Battle%20Royale.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FRiddler%20Battle%20Royale.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Riddler%20Battle%20Royale.ipynb) | 2017 | <b><a href="ipynb/Riddler%20Battle%20Royale.ipynb" title="A puzzle involving allocating your troops and going up against an opponent">Battle Royale</a></b> |
-| [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/CrossProduct.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FCrossProduct.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FCrossProduct.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/CrossProduct.ipynb) | <u>2020</u> | <b><a href="ipynb/CrossProduct.ipynb" title="A puzzle where digits fill a table, subject to constraints on their products">CrossProduct</a></b> |
+| [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/CrossProduct.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FCrossProduct.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FCrossProduct.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/CrossProduct.ipynb) | 2021 | <b><a href="ipynb/CrossProduct.ipynb" title="A puzzle where digits fill a table, subject to constraints on their products">CrossProduct</a></b> |
 | [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/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/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 Puzzle of the Misanthropic Neighbors</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> |
-| [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/war.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2Fwar.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2Fwar.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/war.ipynb) | <u>2020</u> | <b><a href="ipynb/war.ipynb" title="How likely is it to win a game of war in 26 turns?">War. Waht is it Good For?</a></b> |
+| [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/war.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2Fwar.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2Fwar.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/war.ipynb) | <u>2020</u> | <b><a href="ipynb/war.ipynb" title="How likely is it to win a game of war in 26 turns?">War. What is it Good For?</a></b> |
 
 |Run|Year|Word Puzzles|
 |---|----|---|
@@ -78,7 +79,7 @@ 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/Portmantout.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FPortmantout.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FPortmantout.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Portmantout.ipynb) | <u>2020</u> | <b><a href="ipynb/Portmantout.ipynb" title="Find a word that squishes together a bunch of words">World's Shortest Portmantout Word</a></b> |
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/xkcd-Name-Dominoes.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2Fxkcd-Name-Dominoes.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2Fxkcd-Name-Dominoes.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/xkcd-Name-Dominoes.ipynb) | 2018 | <b><a href="ipynb/xkcd-Name-Dominoes.ipynb" title="Lay out dominoes legally; the dominoes have people names, not numbers">xkcd 1970: Name Dominoes</a></b> |
 
-|Run|Year|Probability, Uncertainty, and Counting|
+|Run|Year|Probability and Uncertainty|
 |---|----|---|
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Probability.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FProbability.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FProbability.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Probability.ipynb) | 2018 | <b><a href="ipynb/Probability.ipynb" title="Code and examples of the basic principles of Probability Theory">A Concrete Introduction to Probability</a></b> |
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/ProbabilityParadox.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FProbabilityParadox.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FProbabilityParadox.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/ProbabilityParadox.ipynb) | 2016 | <b><a href="ipynb/ProbabilityParadox.ipynb" title="Some classic paradoxes in Probability Theory, and how to think about disagreements">Probability, Paradox, and the Reasonable Person Principle</a></b> |
@@ -86,8 +87,6 @@ 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/Coin%20Flip.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FCoin%20Flip.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FCoin%20Flip.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Coin%20Flip.ipynb) | 2019 | <b><a href="ipynb/Coin%20Flip.ipynb" title="How to beat the Devil at his own game">The Devil and the Coin Flip Game</a></b> |
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Dice%20Baseball.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FDice%20Baseball.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FDice%20Baseball.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Dice%20Baseball.ipynb) | <u>2020</u> | <b><a href="ipynb/Dice%20Baseball.ipynb" title="Simulating baseball games">Dice Baseball</a></b> |
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Economics.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FEconomics.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FEconomics.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Economics.ipynb) | 2018 | <b><a href="ipynb/Economics.ipynb" title="A simulation of a simple economic game">Economics Simulation</a></b> |
-| [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Euler's%20Conjecture.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FEuler's%20Conjecture.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FEuler's%20Conjecture.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Euler's%20Conjecture.ipynb) | 2018 | <b><a href="ipynb/Euler's%20Conjecture.ipynb" title="Solving a 200-year-old puzzle by finding integers that satisfy a<sup>5</sup> + b<sup>5</sup> + c<sup>5</sup> + d<sup>5</sup> = e<sup>5</sup>">Euler's Sum of Powers Conjecture</a></b> |
-| [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/How%20To%20Count%20Things.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FHow%20To%20Count%20Things.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FHow%20To%20Count%20Things.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/How%20To%20Count%20Things.ipynb) | <u>2020</u> | <b><a href="ipynb/How%20To%20Count%20Things.ipynb" title="Combinatorial math: how to count how many things there are, when there are a lot of them">How to Count Things</a></b> |
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/poker.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2Fpoker.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2Fpoker.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/poker.ipynb) | 2012 | <b><a href="ipynb/poker.ipynb" title="How do we decide which poker hand wins? Several variants of poker are considered.">Poker Hand Ranking</a></b> |
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/risk.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2Frisk.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2Frisk.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/risk.ipynb) | <u>2020</u> | <b><a href="ipynb/risk.ipynb" title="Determining who is likely to win an interminably long game of Risk">The Unfinished Game .... of Risk</a></b> |
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/WWW.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FWWW.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FWWW.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/WWW.ipynb) | 2019 | <b><a href="ipynb/WWW.ipynb" title="Computing the probability of winning the NBA title, for my home town Warriors, or any other team">WWW: Who Will Win (NBA Title)?</a></b> |
@@ -97,10 +96,11 @@ 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/Snobol.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FSnobol.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FSnobol.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Snobol.ipynb) | 2017 | <b><a href="ipynb/Snobol.ipynb" title="As a student, did you ever get a bad grade on a programming assignment? (Snobol, Concordance)">Bad Grade, Good Experience</a></b> |
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/BASIC.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FBASIC.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FBASIC.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/BASIC.ipynb) | 2017 | <b><a href="ipynb/BASIC.ipynb" title="How to write an interpreter for the BASIC programming language">BASIC Interpreter</a></b> |
-| [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Convex%20Hull.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FConvex%20Hull.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FConvex%20Hull.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Convex%20Hull.ipynb) | 2017 | <b><a href="ipynb/Convex%20Hull.ipynb" title="A classic Computer Science Algorithm">The Convex Hull Problem</a></b> |
-| [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/StableMatching.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FStableMatching.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FStableMatching.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/StableMatching.ipynb) | <u>2020</u> | <b><a href="ipynb/StableMatching.ipynb" title="What is the best way to pair up two groups with each other, obeying preferences?">The Stable Matching Problem</a></b> |
+| [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Convex%20Hull.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FConvex%20Hull.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FConvex%20Hull.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Convex%20Hull.ipynb) | 2017 | <b><a href="ipynb/Convex%20Hull.ipynb" title="A classic Computer Science Algorithm">Convex Hull Problem</a></b> |
+| [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/How%20To%20Count%20Things.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FHow%20To%20Count%20Things.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FHow%20To%20Count%20Things.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/How%20To%20Count%20Things.ipynb) | <u>2020</u> | <b><a href="ipynb/How%20To%20Count%20Things.ipynb" title="Combinatorial math: how to count how many things there are, when there are a lot of them">How to Count Things</a></b> |
+| [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/StableMatching.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FStableMatching.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FStableMatching.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/StableMatching.ipynb) | <u>2020</u> | <b><a href="ipynb/StableMatching.ipynb" title="What is the best way to pair up two groups with each other, obeying preferences?">Stable Matching Problem</a></b> |
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Differentiation.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FDifferentiation.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FDifferentiation.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Differentiation.ipynb) | 2017 | <b><a href="ipynb/Differentiation.ipynb" title="A computer algebra system that  manipulates expressions, including symbolic differentiation">Symbolic Algebra, Simplification, and Differentiation</a></b> |
-| [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/TSP.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FTSP.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FTSP.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/TSP.ipynb) | 2018 | <b><a href="ipynb/TSP.ipynb" title="Another of the classics">The Traveling Salesperson Problem</a></b> |
+| [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/TSP.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FTSP.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FTSP.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/TSP.ipynb) | 2018 | <b><a href="ipynb/TSP.ipynb" title="Another of the classics">Traveling Salesperson Problem</a></b> |
 
 
 # Index of Python Files