diff --git a/lectures/_static/lecture_specific/long_run_growth/tooze_ch1_graph.png b/lectures/_static/lecture_specific/long_run_growth/tooze_ch1_graph.png
index c25ac0c4..bb1ace2a 100644
Binary files a/lectures/_static/lecture_specific/long_run_growth/tooze_ch1_graph.png and b/lectures/_static/lecture_specific/long_run_growth/tooze_ch1_graph.png differ
diff --git a/lectures/_static/quant-econ.bib b/lectures/_static/quant-econ.bib
index d288df76..9d0395f7 100644
--- a/lectures/_static/quant-econ.bib
+++ b/lectures/_static/quant-econ.bib
@@ -3,6 +3,31 @@
 Note: Extended Information (like abstracts, doi, url's etc.) can be found in quant-econ-extendedinfo.bib file in _static/
 ###
 
+@book{Burns_2023,
+  title={Milton Friedman: The Last Conservative by Jennifer Burns},
+  author={Burns, Jennifer},
+  year={2023},
+  publisher={Farrar, Straus, and Giroux},
+  address = {New York}
+}
+
+@article{kuznets1939incomes,
+  title={Incomes from independent professional practice, 1929-1936},
+  author={Kuznets, Simon and Friedman, Milton},
+  journal={National Bureau of Economic Research Bulletin},
+  number = {72-23},
+  year={1939},
+  publisher={National Bureau of Economic Research}
+}
+
+@book{friedman1954incomes,
+  title={Income from Independent Professional Practice},
+  author={Friedman, Milton and Kuznets, Simon},
+  year={1945},
+  publisher={National Bureau of Economic Research},
+  address = {New York}
+}
+
 @book{smith2010wealth,
   title     = {The Wealth of Nations: An inquiry into the nature and causes of the Wealth of Nations},
   author    = {Smith, Adam},
diff --git a/lectures/equalizing_difference.md b/lectures/equalizing_difference.md
index 2582c104..bb95bf75 100644
--- a/lectures/equalizing_difference.md
+++ b/lectures/equalizing_difference.md
@@ -18,6 +18,12 @@ kernelspec:
 This lecture presents a model of the college-high-school wage gap in which the
 "time to build" a college graduate plays a key role.
 
+```{note}
+Milton Friedman used our   model  to study whether  differences in the earnings of US dentists and doctors were justified by competitive labor markets or whether
+they reflected entry barriers imposed by US governments working in conjunction with doctors' lobbies.  Chapter 4 of Jennifer Burns {cite}`Burns_2023` presents an 
+interesting account of Milton Friedman's joint work with Simon Kuznets that eventually  led to the publication of {cite}`kuznets1939incomes` and {cite}`friedman1954incomes`. To map  Friedman's application to our model, think of our high school students as Friedman's dentists and our college graduates as Friedman's doctors.  
+```
+
 The model is "incomplete" in the sense that it is just one "condition" in the form of a single equation that would be part of set equations comprising all  "equilibrium conditions" of   a more fully articulated model.
 
 The condition featured in our model determines  a college, high-school wage ratio that equalizes the present values of a high school worker and a college educated worker.