4. Technical: "Minimizing the Adverse Effects of Snow and Ice on Roofs" is a design-oriented article from 2001 available at the US Army Engineer Research and Development Center website. It's not overly technical and provides a good overview of snow and ice issues.
5. Technical:"Snow-Induced Roof Failures and Prevention Methods: An Overview" by Alyssa Stangl is an easy-to-follow technical discussion of the subject. The paper is from from 2013 and available on Failures Wiki: Building, Architectural and Civil Engineering Failures and Forensic Practices.