1. 10year ETIP SNET roadmap 2020-2030, (n.d.).
2. C. Decision, HORIZON 2020 – WORK PROGRAMME 2014-2015 General Annexes, (2014). https://ec.europa.eu/research/participants/data/ref/h2020/wp/2014_2015/annexes/h2020-wp1415-annex-g-trl_en.pdf.
3. Multidisciplinary conceptual design optimization of space transportation systems;Rowell;J. Aircr.,1999
4. I. Tzinis, Technology readiness levels, (2012). https://www.nasa.gov/directorates/heo/scan/engineering/technology/txt_accordion1.html.
5. B. Sauser, J.E. Ramirez-Marquez, R. Magnaye, W. Tan, A systems approach to expanding the technology readiness level within defense acquisition, 2009.