"Don't Know" Item Nonresponse in a Telephone Survey: Effects of Question Form and Respondent Characteristics
研究了电话调查中受访者回答“不知道”的影响因素，发现问题形式和受访者特征（如教育水平）会显著影响无回答率，对改进问卷设计和减少调查偏差有参考价值。
James H. Leigh, Claude R. Martin, Jr., "Don't Know" Item Nonresponse in a Telephone Survey: Effects of Question Form and Respondent Characteristics, Journal of Marketing Research, Vol. 24, No. 4 (Nov., 1987), pp. 418-424