diff --git a/lectures/functions.md b/lectures/functions.md
index 993d0765..65b3b2fc 100644
--- a/lectures/functions.md
+++ b/lectures/functions.md
@@ -74,7 +74,7 @@ str(22)
 type(22)
 ```
 
-The full list of Python built-ins is [here](https://docs.python.org/library/functions.html).
+The full list of Python built-ins is [here](https://docs.python.org/3/library/functions.html).
 
 
 ### Third Party Functions
diff --git a/lectures/numpy.md b/lectures/numpy.md
index 564db8a9..3efbf9fe 100644
--- a/lectures/numpy.md
+++ b/lectures/numpy.md
@@ -1480,9 +1480,9 @@ But this is inefficient relative to computing `Q` once-off.
 A better option is to use descriptors.
 
 A solution from the [quantecon
-library](https://github.com/QuantEcon/QuantEcon.py/tree/master/quantecon)
+library](https://github.com/QuantEcon/QuantEcon.py/tree/main/quantecon)
 using descriptors that behaves as we desire can be found
-[here](https://github.com/QuantEcon/QuantEcon.py/blob/master/quantecon/discrete_rv.py).
+[here](https://github.com/QuantEcon/QuantEcon.py/blob/main/quantecon/discrete_rv.py).
 
 ```{solution-end}
 ```
@@ -1505,7 +1505,7 @@ Your task is to
 
 An example solution is given below.
 
-In essence, we've just taken [this code](https://github.com/QuantEcon/QuantEcon.py/blob/master/quantecon/ecdf.py)
+In essence, we've just taken [this code](https://github.com/QuantEcon/QuantEcon.py/blob/main/quantecon/ecdf.py)
 from QuantEcon and added in a plot method
 
 ```{code-cell} python3
diff --git a/lectures/pandas.md b/lectures/pandas.md
index b43396c0..875d9c52 100644
--- a/lectures/pandas.md
+++ b/lectures/pandas.md
@@ -606,7 +606,7 @@ time from the World Bank.
 
 The World Bank [collects and organizes data](https://data.worldbank.org/indicator) on a huge range of indicators.
 
-For example, [here's](https://data.worldbank.org/indicator/GC.DOD.TOTL.GD.ZS/countries) some data on government debt as a ratio to GDP.
+For example, [here's](https://data.worldbank.org/indicator/GC.DOD.TOTL.GD.ZS) some data on government debt as a ratio to GDP.
 
 The next code example fetches the data for you and plots time series for the US and Australia
 
diff --git a/lectures/python_essentials.md b/lectures/python_essentials.md
index e3c9dc21..e9b252e3 100644
--- a/lectures/python_essentials.md
+++ b/lectures/python_essentials.md
@@ -701,7 +701,7 @@ In programming, as in mathematics, the opposite is true
   reversed would be very hard to read, even if the author told you so on the
   first page.
 
-In Python, the standard style is set out in [PEP8](https://www.python.org/dev/peps/pep-0008/).
+In Python, the standard style is set out in [PEP8](https://peps.python.org/pep-0008/).
 
 (Occasionally we'll deviate from PEP8 in these lectures to better match mathematical notation)
 
diff --git a/lectures/writing_good_code.md b/lectures/writing_good_code.md
index 153eb741..081f2966 100644
--- a/lectures/writing_good_code.md
+++ b/lectures/writing_good_code.md
@@ -133,7 +133,7 @@ axes[2].legend(loc='upper left', frameon=True)
 plt.show()
 ```
 
-True, the code more or less follows [PEP8](https://www.python.org/dev/peps/pep-0008/).
+True, the code more or less follows [PEP8](https://peps.python.org/pep-0008/).
 
 At the same time, it's very poorly structured.