An introduction to "Pennterra" which, Asimov says, "takes up the matter of violence and nonviolence."
| Date | Publication | Publisher | Type | Page | |
|---|---|---|---|---|---|
| September 1987 |
|
Pennterra | Congdon & Weed | Novel | xi |
| October 1988 |
|
Pennterra | Worldwide Library | Novel | 5 |
| December 1988 |
|
Pennterra | New English Library | Novel | xi |
| 1989 |
|
The Tyrannosaurus Prescription and 100 Other Essays | Prometheus Books | Nonfiction | 205|63 |