*A Political History of SF by Eric Raymond*"The Science in Science Fiction" by Brian Stableford, David Langford, & Peter Nicholls (1982)*Kheper Realism scale*The Ascent of Wonder by David G. Hartwell & Kathryn Cramer.
* A Political History of SF by Eric Raymond* "The Science in Science Fiction" by Brian Stableford, David Langford, & Peter Nicholls (1982)* David N. Samuelson, "Hard SF", pp.