| title | ISBN-13 (ISBN-10) | year of publica- tion |
|---|---|---|
| Enrollment Problem: Proven Management Techniques | 978-0-02-915520-2 (0-02-915520-7) | 1987 |
| Some Reasons Why I Am a Freethinker | 978-0-910309-72-1 (0-910309-72-8) | 1993 |
Robert G. Ingersoll · Robert Green, Col. Ingersoll · Robert Green Ingersoll · Robert Ingram · Robert Stewart-Ingersoll