Compilation in Founding Father Letters?

Dear Rich: Universities and libraries often publish the collected papers of long-dead public figures, such as George Washington or Alexander Hamilton. If I quote one of their letters in a book, I'll want to cite the source of the letter that I took from a volume published by, say, a university press. But if I quote excerpts from several letters, do I need to seek permission from the press that compiled them? No, you don't need to seek permission. It's true that copyrights can be granted for compilations of public domain data, and it's also true that the universities that maintain these compilations perform a valuable public service, but we doubt that the collected papers of a founding father illustrate the type of selection and arrangement that rises to a separately protectable copyright. For example, alphabetical and chronological arrangements cannot be protected. All that might be protected are the compiler’s creative selection and arrangement of the letters (not the letters themselves). This is sometimes referred to as a thin copyright and is difficult to enforce.