3 ms·
online copy of the latter: https://space.nss.org/colonies-in-space-by-t-a-heppenheimer/ https://space.nss.org/colonies-in-space-by-t-a-heppenheimer/
by abecedarius 5y ago
online copy of the latter: https://space.nss.org/colonies-in-space-by-t-a-heppenheimer/ https://space.nss.org/colonies-in-space-by-t-a-heppenheimer/
- dredmorbius 5y agoO'Neill's book is at the Internet Archive / Open Library, available for check-out.