Fred,
I see I was wrong about the book Ballad Collectors of North America being out of print. At the price it's being sold for, getting it from your local library may be the way to go. In the USA, most libraries can get you a copy of almost any book you're interested in even if they don't have it in their collection. My public library has gotten many books for me that were almost only available from college libraries through what is called "interlibrary loan."
Jim