Five brief philosophical essays.
| Date | Publication | Publisher | Type | Page | |
|---|---|---|---|---|---|
| 1962 |
|
Letters from the Earth | Harper & Row | Collection | 209 |
| September 1963 |
|
Letters from the Earth | Crest Books / Fawcett World Library | Collection | 166 |
| 1970 |
|
Letters from the Earth | Fawcett Crest | Collection | 166 |