1. J. M. Wheatley, T. Xiang, Stability of d-wave pairing in 2 dimensions, Solid State Communications 88 (1993) 593-595.
2. T. Xiang, G. A. Gehring, Numerical solution of S=1 antiferromagnetic spin chains using a truncated basis expansion, Physical Review B 48 (1993) 303-310.