Patrick Gray thinks this is interesting: Levels and types of requirements From 1. The essential software requirement from Software Requirements by Karl E Wiegers and Joy Beatty Publisher: Microsoft Press Released: August 2013 Note Note read this far for requirements study. Share this highlight http://www.safaribooksonline.com/a/software-requirements/9072/ Twitter Facebook Google Plus Email Get Instant Access Now Start a Free Trial Learn about Safari for Business Have an account? Sign in. Minimise Unlock the rest of Software Requirements and 30,000 other books and videos By clicking this box, you confirm that you have read and agree to the terms and conditions of our Membership Agreement, and you understand that when your trial period ends, you will be required to provide billing information if you wish to continue using the service. Unlock the rest of this book Start a Free 10-Day Trial loading Learn about Safari for Business Have an account? Sign in.