determiner , pronoun ~ of (~ of them)
USAGE NOTE: The use of the preposition of is necessary when a pronoun follows. When a noun follows, the use of of the limits the meaning--we saw ~ students; we saw ~ of the students whom we had met earlier.
MANY
Meaning of MANY in English
The Bbi combinatory dictionary of English, a guide to word combinations. Комбинаторный словарь английского языка Bbi. Руководство по словосочетаниям. 2012