Comma Sense Quotes

“The students’ love of punctuation is boundless. To form the possessive of plural nouns that don’t end in s, add an apostrophe and s: The men’s love of punctuation is boundless. If two or more people possess the same thing, you need only put the apostrophe after the last one of the two mentioned: Len and Barry’s seminar teaches a love of punctuation. if two people own items individually, you must show your respect by giving them each an ’s: Len’s and Barry’s wives love punctuation. The possessive form of it is spelled its: The level of a civilization is measured by the precision of its punctuation.”
― Richard Lederer, Comma Sense: A Fun-damental Guide to Punctuation

“The Apostrophe To grant possession to a singular noun, simply add an apostrophe and s: The student’s love of punctuation is boundless. If a plural noun that already ends in s needs to become possessive, slap a single apostrophe on the end of that word:”
― Richard Lederer, Comma Sense: A Fun-damental Guide to Punctuation