Generic Programming in Concept C++
cppreference - Library Concepts
cppreference - Constraints and concepts
Wikipedia - Concepts (C++)
C++0x Concepts — Historical FAQs
N4553 - Working Draft, C++ extensions for Concepts
[2013] Concepts Lite: Constraining Templates with Predicates—Andrew Sutton, Bjarne Stroustrup
[2010] C++ Concepts: a Postmortem