Order parameters in X X Z -type spin 1 2 quantum models with Gibbsian ground states. Skrypnik, Wolodymyr — 2006 SIGMA. Symmetry, Integrability and Geometry: Methods and Applications [electronic only]
Three order parameters in quantum X Z spin-oscillator models with Gibbsian ground states. Dorlas, Teunis C.; Skrypnik, Wolodymyr I. — 2008 SIGMA. Symmetry, Integrability and Geometry: Methods and Applications [electronic only]