Sentence:  Let us now glance at the demonstrative and relative pronouns. Of the former there are but two in English, "this" and "that", with their plural forms, "these" and "those". To them, American adds a third, "them", which is also the personal pronoun of the third person, <WSD>objective</WSD> case. 
Meaning of the word marked with <WSD> tags:  Of, or relating to a noun or pronoun used as the object of a verb.