slides: add reference for HSM

slides/sections/0.md

@@ -24,7 +24,7 @@ references:
     author:
       family: Trapani
       given: Lorenzo
-    title: testing for (in)finite moments
+    title: Testing for (in)finite moments
     container-title: Journal of Econometrics
     issued:
       year: 2015
@@ -37,6 +37,20 @@ references:
     issued:
       year: 1986
 
+  - id: robertson74
+    type: article-journal
+    author:
+    - family: Robertson
+      given: Tim
+    - family: Cryer
+      given: Jonathan D
+    issued:
+      - year: 1974
+    title: An iterative procedure for estimating the mode
+    container-title: Journal of the American Statistical Association
+    volume: 69
+    issue: 348
+
 header-includes: |
   ```{=latex}
   %% Colors

slides/sections/4.md

@@ -80,14 +80,12 @@ How to estimate sample median, mode and FWHM?
 
 ## Sample mode
 
-Most probable value
+Half Sample Mode[@robertson74]
 
-. . .
 
-Half Sample Mode
-
-- Iteratively identify the smallest interval containing half points
-- Once the sample is reduced to less than three points, take average
+- Find the smallest interval containing half points
+- Repeat
+- If the sample has less than three points, take average
 
 . . .