Qiang Duan, : 'Network-as-a-Service and network cloudification in the next generation Internet' (Telecommunications, 2017), 'Network as a Service for Next Generation Internet', Chap. 1, pp. 1-24, DOI: 10.1049/PBTE073E_ch1
IET Digital Library, https://digital-library.theiet.org/;jsessionid=7st9jc053jset.x-iet-live-01content/books/10.1049/pbte073e_ch1