| title | ISBN-13 (ISBN-10) | year of publica- tion | other author(s) |
|---|---|---|---|
| Combinatorics of Train Tracks. | 978-0-691-02531-5 (0-691-02531-2) | 1991 | |
| Combinatorics of Train Tracks. , Volume 125 | 978-0-691-08764-1 (0-691-08764-4) | 1992 | John L. Harer |
| Discrete Mathematics: Proof Techniques and Mathematical Structures | 978-981-02-4088-2 (981-02-4088-0) | 1999 | |
C.P. · R. C. · R. P. · Robert C. Penner · Robert Clark Penner