@article {10804,
	title = {Quantized Hall effect and quantum phase transitions in coupled two-layer electron systems},
	journal = {Physical Review B},
	year = {1993},
	pages = {4394-4412},
	doi = {10.1103/PhysRevB.47.4394},
	author = {Song He and S. Das Sarma and X.C. Xie}
}
