Relative proN in phrases of quantity and quality => non-defining clauses(,)
1) quantifier (some, each, all) + of WHOM/ WHICH
Ex: The members of the special commission on crime,some of whom were appointed by the mayor,meet weekly. :!: Buộc dùng ,
2) the superlative/ ordinal form (the first, the best) + of WHOM/WHICH
Ex: This term we have eight courses, the easiest of which is AG
:pencil2: Relative C phải nằm sát N, proN mà nó bổ nghĩa.