@conference {1277,
	title = {Incorporating the Sympson-Hetter exposure control method into the a-stratified method with content blocking},
	booktitle = {Paper presented at the annual meeting of the American Educational Research Association},
	year = {2002},
	note = {PDF file, 387 K},
	address = {New Orleans, LA},
	author = {Yi, Q.}
}
