I used this booklet as a reference while writing a paper in high school about Bucks County rail history. The Spruance Library in Doylestown (at the Mercer Museum) had a copy. It was called "Happy Birthday, Newtown Railroad!", I think. At the time you had to become a member to use the library, which for student-version of me in 1991 was $10. The Phila NRHS library probably has a copy too. The Newtown Historic Association may have one also.
My paper was part of a scholarship competition by the Bucks County Chamber of Commerce. Years later I picked up a book on rail abandonments in the eastern US, hoping to find more bits of information for my efforts at modeling the Newtown Branch. Sure enough, the PN&NY merited a chapter. I eagerly turned to the Sources and Further Reading section at the back...to find my name and a citation of my paper.
"Am Gleis drei bitte einsteigen - Türen schliessen selbsttätig. Vorsicht bei der Abfahrt!"