Reference [8] of the following paper:

Chi-Hang Fred Fung, Wei Yu and Teng Joon Lim, "Precoding for the Multi-Antenna Downlink: 
Multi-user Gap Approximation and Optimal User Ordering", IEEE Transactions on Communications,
vol. 55, no. 1, pp. 188-197, January 2007.

should have been:

[8] M. Schubert and H. Boche, "Iterative multiuser uplink and downlink beamforming under 
SINR constraints", IEEE Transactions on Signal Processing, vol.53,  no.7,  pp.2324 - 2334,
July 2005. 

The title of the paper was incorrected stated.