“…The suggestion of [72] to apply subset systems to the theory of continuous posets was followed by Nelson [51], Novak [55], Bandelt [6], Bandelt and Erné [7], [8], and this research was carried on by Venugopalan [70], [71], Xu [73], Baranga [9], Menon [49], Shi and Wang [65], Erné [20], [23] among others. Conditions iq and iiq together ensure that each ZrP s contains all singletons.…”