во-первых, во-вторых, в-третьих ...

• Three features must be pointed out. First(ly), we must recognize ... Second(ly), ... Third(ly), ...

• For one thing (or On the one hand), the susceptibility is low after cooling; for another [or on the other (hand)], this cooling rate seems too high to permit ...

• In the first place, two major types exist; second, closer examination discloses that ...