| The “cup of tea” problem | |
| Mostly Harmless, by Douglas Adams | |
| The Hitchhiker's Guide to the Galaxy: A Trilogy in Four Parts, by Douglas Adams | |
| So Long, and Thanks for All the Fish, by Douglas Adams | |
| Life, the Universe and Everything, by Douglas Adams | |
| The Restaurant at the End of the Universe, by Douglas Adams | |
| The Hitchhiker’s Guide to the Galaxy, by Douglas Adams | |