* German military firearms and ammunition of World War II: This is his most prominent area of expertise. He has written several books on the topic, including "German Military Handguns 1871-1945," "German Military Small Arms 1871-1945," and "German Small Arms Ammunition 1871-1945."
* Other military firearms and ammunition: Angolia's work also encompasses other nations and eras, including American, British, and Soviet military firearms and ammunition.
He is considered a leading authority on this subject and his books and articles are widely recognized for their comprehensive research and detailed information.
It is important to note that while John R. Angolia is known for his work on military firearms and ammunition, he may have written on other topics as well. To be completely sure, you could search online for his name or look for his work in a library catalog.