How do you form possessive of a plural noun that does not end in s?

Plural possessive nouns that do not end in -s are formed by adding an apostrophe -s ('s) to the end of the Word. Examples:

• a child's, the children's playground
• a goose's, the geese's pond
• a man's, the men's department
• an ox's, the oxen's yoke
• a sheep's, the sheep's pasture