Apostrophe & Words Ending with s
This is a rather controversial rule.
The most convincing and widely acceptable rule is that every proper noun ending with an s shall not have an additional s after the apostrophe, when denoting a possessory form.
For example: Jesus', Jones'.
As with common nouns, if used in singular form, an additional s shall follow after the apostrophe.
For example: class's, glass's, actress's.
However, if a common noun is used in a plural form, there shall be no s after the apostrophe.
For example: classes', boys', dogs'.
