*David G. Hartwell, "Hard Science Fiction,", Introduction to "The Ascent of Wonder: The Evolution of Hard Science Fiction", 1994, ISBN 0-312-85509-5*Kathryn Cramer's chapter on hard science fiction in" The Cambridge Companion to SF", ed.
* David G. Hartwell, "Hard Science Fiction,", Introduction to "The Ascent of Wonder: The Evolution of Hard Science Fiction", 1994, ISBN 0-312-85509-5* Kathryn Cramer's chapter on hard science fiction in "The Cambridge Companion to SF", ed.