Peter Z. Cohen
Below is a pamphlet preserved in Pickler Memorial Library's Special Collections department pertaining to one of the six authors invited to Truman's first ever Children's Literature Festival. Information pertaining to the planning of each festival is often what falls into the library's safekeeping, and especially for the festival years before the internet made it possible to look up authors on a computer rather than keep hard copies of their biographies.
On a list describing the 1983 author arrangement, it says about Peter Z. Cohen: "Most of his books are horse stories or 'outdoor' activity books." A transcript of his pamphlet can be found at the provided link.