8.7.4 Joint Possession
When joint possession is being shown with nouns, or with an organization’s or business firm’s name, use the possessive form only in the last word of the noun or name.
Food and Drug Administration’s policy
Farrar, Straus & Giroux’s books
Centers for Disease Control and Prevention’s Task Force
When possession is individual, each noun takes the possessive form.
Hammond and Horn’s study
We matched the infant’s and mother’s records.
Note: When one of the nouns takes a possessive pronoun, the other nouns take the possessive as well.
I presented the intern’s and my workups.