Nigg, Claudio R, Robert W. Motl, Kristin T. Wong, Lisa U. Yoda, Dana K. McCurdy, Raheem Paxton, Caroline C. Horwath, and Rod K. Dishman. 2009. “Impact of Mixed Survey Modes on Physical Activity and Fruit Vegetable Consumption: A Longitudinal Study”. Survey Research Methods 3 (2):81-90. https://doi.org/10.18148/srm/2009.v3i2.1092.