You get closer to something bijective when you only consider lemmas, but then you'll probably have around 1/3 that are bijective, 1/3 that 1->2 or 3 and 1/3 tha

You get closer to something bijective when you only consider lemmas, but then you'll probably have around 1/3 that are bijective, 1/3 that 1->2 or 3 and 1/3 that are 2 or 3->1.