Agile Modeling: Introduction to User Stories
Mike Cohn’s Blog: Non-functional Requirements as User Stories
wikiwiki: Non Functional Requirements
Agile Coaching: Non-Functional Requirements: are user stories useful?
Artima: Johan Peeters: Dreams and Nightmares
Representing non-functional requirements is tricky. There are two kinds of non-functional requirement as mentioned in the aquis piece: independent, and distributed. When faced with a distributed non-functional requirement, adding it to your ‘definition of done‘ is called for. As you can tell by the links, there seems to be some difference in opinion in handling ‘independent’ non-functional requirements.
If you have pointers, please share in my comments. And thanks for the input in advance.