When different things belong to different owners, an apostrophe (') and an -s are added to each noun in the sentence, depending on whether the noun is singular or plural.

• The notebooks of Maria and the paper of Chris are in the shelf.

• Maria's notebooks and Chris's paper are in the shelf.

• The books of Peter and Matthew are on the table.

• Peter's and Matthew's books are on the table.

When the same thing belongs to different owners, an apostrophe (') and an -s are added only to the last noun.

• The new computer unit of Jean and Jovy was delivered by Mark.

• Jean and Jovy's new computer unit was delivered by Mark.