##[]A |= []B
[]A |= <>B
<>A |= []A
##[]A |= A
<>A |= A			# @fixme true?
##A |= <>A			# ??

##|= [](A|B) -> ([]A|[]B)		# not even in S5
##|= (<>A&<>B) -> (<>A&<>B)	# not even in S5