Robert H. · Robert Hamma · Robert M.
BookSurge Publishing · Sorin Books
| title | ISBN-13 (ISBN-10) | year of publica- tion |
|---|---|---|
| Earth's Echo: Sacred Encounters With Nature | 978-1-893732-46-9 (1-893732-46-0) | 2002 |
| Landscapes of the Soul: A Spirituality of Place | 978-1-4196-5939-3 (1-4196-5939-1) | 2007 |