Is it better to have models that have double faces or is it better to have a two-sided material instead? - Pipeline & Plugins - Epic Developer Community Forums
Two sided material in Blender - Manandari.com
normals - Disable double sided faces in Blender 3D View - Blender Stack Exchange
Blender Sushi: December 2011
how to create double sided materials in blender - YouTube
Two-sided Meshes, Normal & Shininess – Blender Knowledgebase