From 0787324d1ea898e880abf3999a72b46d7d29b9f9 Mon Sep 17 00:00:00 2001
From: Antti H S Laaksonen <ahslaaks@cs.helsinki.fi>
Date: Sat, 25 Feb 2017 21:59:02 +0200
Subject: [PATCH] References etc.

---
 chapter23.tex | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/chapter23.tex b/chapter23.tex
index 82d27f6..5b5d0e1 100644
--- a/chapter23.tex
+++ b/chapter23.tex
@@ -749,7 +749,8 @@ $2 \rightarrow 1 \rightarrow 4 \rightarrow 2 \rightarrow 5$.
 \index{Kirchhoff's theorem}
 \index{spanning tree}
 
-\key{Kirchhoff's theorem} provides a way
+\key{Kirchhoff's theorem}\footnote{G. R. Kirchhoff (1824--1887) was
+a German physicist.} provides a way
 to calculate the number of spanning trees
 of a graph as a determinant of a special matrix.
 For example, the graph