diff --git a/tech/error_handling.wiki b/tech/error_handling.wiki
index 6106666..da105cb 100644
--- a/tech/error_handling.wiki
+++ b/tech/error_handling.wiki
@@ -1,5 +1,15 @@
 = Error Handling =
 
+Key points
+
+* humans are the most unpredictable part of any system and therefore the most
+  difficult to model for design
+* humans have higher failure rates unde rhigh sctress levels, but are more
+  flexible in recovering form emergegeny situations and the last hope in a
+  potential disaster
+* there is a tradoff between making the HCI easy and intutive, and ensuring the
+  system safety is not comprimised by a cocky operator
+
 == Types of human error ==
 
 * slips
diff --git a/tech/graphics.wiki b/tech/graphics.wiki
index ed77b8e..0566c4e 100644
--- a/tech/graphics.wiki
+++ b/tech/graphics.wiki
@@ -4,6 +4,10 @@ Computer graphics is the field focusing on making a computer generate an image.
 
 == User interfaces ==
 
+Also see ISO 9241-11: Guidance on usability (98) and
+ISO/IEC 9126: Software product evaulation - Quality characteristics and
+guidelines for their use (91)
+
 * [[8_rules_ui]]
 * [[usability_heuristics]]
 * [[human_limitations]]