In The Place Inside the Storm, Tara reads "an old SciFi novel from the nineteen-seventies" that contains the line The unforetold, the unproven, that is what life is based on...
Joel Suzuki: In Ballad of the Bluerock, Suzi tells Joel that she likes science fiction, and one of the books she's reading is The Left Hand of Darkness.
In Eclipse Phase, one of the setting books mention a space habitat where everyone is sleeved in a gender-bending body, like the Gethenians. It's called Winter. When a confused fan asked the developers where the name came from, they cheerfully admitted it.