@article {507,
	title = {Constraint-weighted a-stratification for computerized adaptive testing with nonstatistical constraints: Balancing measurement efficiency and exposure control},
	journal = {Educational and Psychological Measurement},
	volume = {69},
	year = {2009},
	pages = {35-49},
	author = {Cheng, Y and Chang, Hua-Hua and Douglas, J. and Guo, F.}
}
