Bantam Books | Northrop X-4 Bantam | Spectra Records | RCA Spectra 70 | Optare Spectra | NMR spectra database | Kia Spectra |
The first four books in the series were published by Bantam Books imprint Bantam Spectra, but after the publisher dropped the series Pratt continued publishing the remainder of the series first through serialized versions and reader donations and then through successful Kickstarter campaigns.