period@@1	period	time	29
period@@1	period	era	21
period@@1	period	interval	9
period@@1	period	age	8
period@@1	period	stage	8
period@@1	period	time frame	7
period@@1	period	cycle	6
period@@1	period	day	6
period@@1	period	time period	5
period@@1	period	phase	4