Nath, R., Kasinathan, D., Rosner, H., Baenitz, M., & Geibel, C. (2008). Electronic and magnetic properties of K2CuP2O7: A model S = ½ Heisenberg chain system. Physical Review B, 77: 134451, pp. 134451-1-134451-8. doi:10.1103/PhysRevB.77.134451.