diff --git a/system theoretic process analysis.md b/system theoretic process analysis.md
index c407e220d..1b951c2ed 100644
--- a/system theoretic process analysis.md	
+++ b/system theoretic process analysis.md	
@@ -30,6 +30,6 @@
 	- step three: [[identify unsafe control actions]]
 		- an [[unsafe control action]] is one that, in a particular context, will lead to a [[hazard]].
 		- it must include the actual (real) context in which the control action is unsafe, instead of controller beliefs; and it must be linked to a hazard.
-		- define [[controller constraints]]: behaviours that need to be satisfied to prevent UCAs.
+		- define [[controller constraints]]: behaviours that need to be satisfied to prevent UCAs. they can usually be derived from negations of the UCAs.
 		
 	
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