--- a/discussion.roff	Sun Jul 15 20:00:14 2012 +0200
+++ b/discussion.roff	Sun Jul 15 21:57:51 2012 +0200
@@ -602,6 +602,19 @@
 There is the cost of code complexity to be able to customize.
 There is the cost of less tested setups, because there are
 more possible setups and especially corner cases.
+Steve Johnson confirms:
+.[ [
+eric raymond the art of unix programming
+.], p. 233]
+.QS
+Unless it is done very carefully, the addition of an on/off
+configuration option can lead to a need to double the amount of
+testing. Since in practice one never does double the amount of testing,
+the practical effect is to reduce the amount of testing that any
+given configuration receives. Ten options leads to 1024 times as much
+testing, and pretty soon you are talking real reliability problems.
+.QE
+.LP
 Additionally, there is the cost of choice itself.
 The code complexity directly affects the developers.
 Less tested code affects both users and developers.
@@ -4074,7 +4087,6 @@
 .BP input/deps-mmh.eps .8i
 .EP
 
-The figures display all program to source file relationships
-that are not one-to-one,
-i.e. all programs that are built from multiple source files.
+The figures display all program to source file relationships where
+programs (ellipses) are built from multiple source files (rectangles).
 The primary source file of each program is omited from the graph.