diff --git a/01-one.md b/01-one.md
index ca4dc268d6b1539b9c418bc9c33993ebebd9c70e..3f14912a5a5a2a706486bc79b4dfa53e00bf0517 100644
--- a/01-one.md
+++ b/01-one.md
@@ -9,7 +9,8 @@ minutes: 10
 > * Learning objective 1
 > * Learning objective 2
 
-Paragraphs of text --- possibly including **definitions** ---
+Paragraphs of text
+--- possibly including [key word 1](reference.html#key-word-1) ---
 mixed with:
 
 ~~~ {.python}
diff --git a/02-two.md b/02-two.md
index 0412d1bb186e0dc2d7bba0c31f4d1b0c242f6441..dfd513a4ad05bd9c0d4a7350c8d7dec7da153d27 100644
--- a/02-two.md
+++ b/02-two.md
@@ -9,7 +9,8 @@ minutes: 10
 > * Learning objective 1
 > * Learning objective 2
 
-Paragraphs of text --- possibly including **definitions** ---
+Paragraphs of text
+--- possibly including [key word 2](reference.html#key-word-2) ---
 mixed with:
 
 ~~~ {.python}
@@ -34,4 +35,5 @@ and possibly including:
 > ## Challenge Title {.challenge}
 >
 > Description of a single challenge.
-> There may be several challenges.
+> There may be several challenges
+> that make reference to [Challenge Title](01-one.html#challenge-title).
diff --git a/reference.md b/reference.md
index 8d0c4fe2df8699275b7a4eed2321c4a4af7ece2f..b202f9d13366a0fca762f9e758e0d05f784ddc88 100644
--- a/reference.md
+++ b/reference.md
@@ -13,8 +13,8 @@ subtitle: Reference
 
 ## Glossary
 
-Key Word 1
+key word 1
 :   Definition of first term
 
-Key Word 2
+key word 2
 :   Definition of second term