What has the author Charles Grant Robertson written?

There are two authors named Charles Grant Robertson, and it's unclear which one you're referring to.

To help me determine which one you mean, could you please provide more context? For example:

* What is the general topic of their writing? Is it history, fiction, or something else?

* Do you know any specific titles of their work?

* What time period are you interested in?

Once you provide more information, I can assist you in finding the specific author and their works.