Part of writing also includes punctuation. Cec Murphy recently ran a series on apostrophes that some of you might find helpful.
The possessive of most singular nouns is formed by adding an apostrophe and an s. Except for a few irregular plurals that don’t end in s, the possessive of plural nouns is formed by adding an apostrophe only.
* the horse’s mouth, a bass’s stripes, puppies’ paws, children’s literature.
This general rule covers most proper nouns, including names ending in s, x, or z, and both are singular and plural forms, as well as letters and numbers. Click here to read the rest of the article and the entire series.