Identify the unclear pronoun references in the following paragraph. Rewrite the sentences to make the pronoun references clear and underline the changes. Books are the medium through which human beings talk with enlightened minds, the great men of the world. They are our best friends. They introduce them to the life and the world. Books are the mirrors of past, present and even future. These are having an active voice. We know about the thoughts and deeds of our ancestors through it. They make the noble men alive in the world forever.