aggregate:
	cat obs{a,p}t/item | sort -t@ -n > obsapt/item
	cat obs{a,p}e/item | sort -t@ -n > obsape/item
	cat obs{a,p}{t,e}/item | sort -t@ -n > obsap/item
	cat bs{a,p}/item | sort -t@ -n > bsap/item
	cat bs{a,p,e}/item | sort -t@ -n > bsape/item