Where to put apostrophe with s after two proper nouns joined by and?

When two proper nouns are joined by "and," you typically place the apostrophe with "s" after the second noun to indicate joint possession. For example, if you want to indicate that a book belongs to both John and Mary, you would write "John and Mary's book." If each person owns separate items, you would add an apostrophe with "s" to both names, as in "John's and Mary's books."