I wrote a paper on this a number of years ago. Here were my primary sources: https://arxiv.org/abs/cs/0007021 https://arxiv.org/abs/cs/0007021 https://arxiv.o

I wrote a paper on this a number of years ago. Here were my primary sources: https://arxiv.org/abs/cs/0007021 https://arxiv.org/abs/cs/0007021 https://arxiv.org/abs/1203.1895 https://arxiv.org/abs/1203.1895 I believe the second depends on the first.