| ▲Título▼ | ▲C▼ | ▲Año▽ | ▲V▼ | ▲Concepto▼ |
|---|---|---|---|---|
| Miskatonic University Graduate Kit (junto a Lisa A. Free, Ron Leming, Sandy Petersen et al.) |   | 1987 | — | Escritor |
| Introduction (to "Cthulhu Companion") (junto a Sandy Petersen) |  | 1983 | — | Escritor |
| Sourcebook for the 1920s (junto a Tadashi Ehara, Harry Henderson, Steve Perrin et al.) |  | 1981 | — | Escritor |
| Eastern U.S. Rail Lines, 1920s |   | 1981 | — | Escritor |
| Call of Cthulhu World Map (Foldout) (junto a Lynn Willis) | | 1981 | — | Escritor |
