Update choropleth-maps.md

Author: LiamConnors

doc/python/choropleth-maps.md

@@ -216,7 +216,7 @@ In **Plotly.py 6.3 and later**, the built-in countries geometry is created from
 
 In **earlier versions of Plotly.py**, the built-in countries geometry is based on Natural Earth data only. Plotly includes data from Natural Earth "as-is". This dataset draws boundaries of countries according to de facto status. See the [Natural Earth page for more details](https://www.naturalearthdata.com/downloads/50m-cultural-vectors/50m-admin-0-countries-2/).
 
-To use the built-in countries geometry, provide `locations` as [three-letter ISO country codes](https://en.wikipedia.org/wiki/ISO_3166-1_alpha-3).
+To use the built-in countries geometry, provide `locations` as [three-letter ISO country codes](/python/outline-map-locations/#supported-iso-codes).
 
 ```python
 import plotly.express as px
@@ -229,7 +229,7 @@ fig = px.choropleth(df, locations="iso_alpha",
 fig.show()
 ```
 
-To use the USA States geometry, set `locationmode='USA-states'` and provide `locations` as two-letter state abbreviations:
+To use the USA States geometry, set `locationmode='USA-states'` and provide `locations` as [two-letter state abbreviations](/python/outline-map-locations/#supported-us-state-codes):
 
 ```python
 import plotly.express as px