7. Do not use the personal pronoun form them for the adjective those: [Those books are mine].
+35. Compound Personal Pronouns.+—To the personal pronouns my, our, your, him, her, it, and them, the syllables self (singular) and selves (plural) may be added, thus forming what are termed compound personal pronouns. These pronouns have only two uses:—
1. They are used for emphasis: [He himself is an authority on the subject].
2. They are also used reflexively: [The boy injured himself].
+36. The Relative or Conjunctive Pronouns.+—The pronouns who, which, what (= that which), that, and as (after such) are more than equivalents for nouns, inasmuch as they serve as connectives. They are often named relative pronouns because they relate to some antecedent either expressed or implied; they are equally well named conjunctive pronouns because they are used as connectives. They introduce subordinate clauses only; these clauses are called relative clauses, and since they modify substantives, are also called adjective clauses.
+37. Uses of Relative Pronouns.+—Who is used to represent persons, and objects or ideas personified; which is used to represent things; that and as are used to represent both persons and things.
When a clause is used for the purpose of pointing out some particular person, object, or idea, it is usually introduced by that; but when the clause supplies an additional thought, who or which is more frequently used. The former is called a restrictive clause, and the latter, a non-restrictive clause.
[The boy that broke his leg has fully recovered (restrictive).] Note the omission of the comma before that. [My eldest brother, who is now in England, will return by June (non-restrictive).] Note the inclosure of the clause in commas. See Appendix 5, rule 10.
In the first sentence it is evident that the intent of the writer is to separate, in thought, the boy that broke his leg from all other boys. Although the clause does indeed describe the boy's condition, it does so for the purpose of limiting or restricting thought to one especial boy among many. In the second sentence the especial person meant is indicated by the word eldest. The clause, who is now in England, is put in for the sake of giving an additional bit of information.
+38. Constructions of Relative Pronouns.+—Relative pronouns may be used as subject, object, object of a preposition, subject of an infinitive, and possessive modifier.