In post #549 here I answered: And then I was surprised by the comment of Tom, asking how the pairing was done. Well, I thought that I had discussed it in some thread in BSM, but after looking at it, it seems that I did only a few sparse remarks here and there. On other hand, people was not liking to interrupt the flow of the thread and I have been either contacted privately or suggested to open a new thread. So here it is. The development can be traced in some draft papers: http://arxiv.org/abs/hep-ph/0512065 http://arxiv.org/abs/0710.1526 http://arxiv.org/abs/0910.4793 http://www.vixra.org/abs/1102.0034 Next post is my answer to Tom question. Keep in mind that we produce squarks, while the quarks are just the ingredient to terminate the extremes of the string.