Technology Readiness Levels—A White Paper
Mankins, J. 1995. Technology Readiness Levels—A White Paper. Washington, DC, USA: Advanced Concepts Office, Office of Space Access and Technology, National Aeronautics and Space Administration (NASA).
This source is considered a primary reference for the Product Systems Engineering Special Activities article.
This paper presents a systematic metric/measurement system that helps in assessing the maturity of a particular technology and provides a comparison of maturity levels between different types of technology.