Nucleon structure; proceedings of the international conference at Stanford University, June 24-27, 1963.

1964 Evidence for a MOLECULAR Structure of Mesons

Nucleon Structure, edit. by Hofstadter & Schiff
Though I have not read this book I have studied the theoretical work of one of the contributors to it, Dr. Ernest Sternglass, who collaborated with one of the editors, Robert Hofstadter, during the 1950s, at Stanford University, doing research which led to a Nobel prize for Hofstadter in 1961. I was 13 years old at that time, and had never heard of Sternglass or Hofstadter.
The book is basically a collection of the presentations by many different researchers at a conference at Stanford which happened during June 24-27 of 1963. Sternglass's contribution is a chapter titled "Evidence for a Molecular Structure of Heavy Mesons" and starts on page 340. The research which Sternglass and Hofstadter did together, mentioned above, made use of one of the first particle accelerators ["atom smashers"] powerful enough to see inside protons and neutrons. This machine was 150 feet long, and located at Stanford.
In his book Sternglass describes the results of this research, which was to discover that there are several different areas inside protons and neutrons where one finds both electrical and magnetic fields. Everybody involved in the research agreed that this was a strong indication that both protons and neutrons are complex objects, composed of smaller, more fundamental, objects. Because if protons and neutrons were/are simple objects, i.e., fundamental particles, then one would expect the electrical and magnetic fields to be concentrated at the center rather than in several different places.
Sternglass went on to develop a theory (i.e., a "model" --- as all the koool dudes say) to explain the structure of protons and neutrons (hint: they have almost identical structures), and summarized this theoretical work in a 1997 book titled BEFORE THE BIG BANG. But the model was only partially developed in 1964, when this book was published. I reckon that in his contribution to the book Sternglass talks about how he had by then worked out models for the structures of pi-mesons and mu-mesons (hint: they have almost identical structures), as well as some of the other unstable particles which scientists had discovered, such as the K-meson and the lambda, which is a baryon.
If anybody knows where I can find a copy of this book on-line, please email me: MARK dot CREEKWATER at gmail.

Sincerely, Mark Creek-water Dorazio, amateur physics enthusiast