11E04 06A07 2 Tits quadratic form 2 minimax equivalence 2 0-isomorphism 1 11E10 1 16K20 1 Brauer group 1 P-critical poset 1 \(P\)-critical poset 1 almost positive poset 1 conic bundle 1 minimax \(d\)-system of generators 1 minimax system of generators 1 positive poset 1 principal poset 1 quaternion algebra 1 ramification 1