diff --git a/Lib/datetime.py b/Lib/datetime.py
index b9719cbb48d..2f9421829e5 100644
--- a/Lib/datetime.py
+++ b/Lib/datetime.py
@@ -896,6 +896,7 @@ class date:
 
         ISO calendar algorithm taken from
         http://www.phys.uu.nl/~vgent/calendar/isocalendar.htm
+        (used with permission)
         """
         year = self._year
         week1monday = _isoweek1monday(year)
diff --git a/Lib/encodings/hp_roman8.py b/Lib/encodings/hp_roman8.py
index 23342088127..58de1033c13 100644
--- a/Lib/encodings/hp_roman8.py
+++ b/Lib/encodings/hp_roman8.py
@@ -5,6 +5,8 @@
     Original source: LaserJet IIP Printer User's Manual HP part no
     33471-90901, Hewlet-Packard, June 1989.
 
+    (Used with permission)
+
 """#"
 
 import codecs
diff --git a/Lib/unittest/__init__.py b/Lib/unittest/__init__.py
index f6d7ae278ba..7f61a80ff4a 100644
--- a/Lib/unittest/__init__.py
+++ b/Lib/unittest/__init__.py
@@ -1,6 +1,6 @@
 """
 Python unit testing framework, based on Erich Gamma's JUnit and Kent Beck's
-Smalltalk testing framework.
+Smalltalk testing framework (used with permission).
 
 This module contains the core framework classes that form the basis of
 specific test cases and suites (TestCase, TestSuite etc.), and also a