He S, Sarma DS, Xie XC. Quantized Hall effect and quantum phase transitions in coupled two-layer electron systems. Physical Review B. 1993;(8):4394-4412.

Xie XC, Sarma DS, He S. Elementary excitations in a finite fractional quantum Hall droplet. Physical Review B. 1993;(23):15942-15945.

Xie XC, Sarma DS, He S. Magneto-optical spectra of strongly correlated electrons in nonparabolic quantum dots. Physical Review B. 1993;(11):8454-8457.