my talk will be in (three) parts: first ................. second .............. third (in the firs part. .............. then in the second part. finally.
My talk will be in (three), parts: First . . . . . . . . . . . . . . . . . Second . . . . . . . . . . . . . . Third (In the firs part . . . . . . . . . . . . . . Then in the second part. Finally