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Ryan, Declan J., Jorgen A. Wullems, Georgina K. Stebbings, Christopher I. Morse, Claire E. Stewart, i Gladys L. Onambele-Pearson. "Reliability and Validity of the International Physical Activity Questionnaire Compared to Calibrated Accelerometer Cut-off Points in the Quantification of Sedentary Behaviour and Physical Activity in Older Adults." PLoS One 2018.

Ryan, Declan J., et al. "Reliability and Validity of the International Physical Activity Questionnaire Compared to Calibrated Accelerometer Cut-off Points in the Quantification of Sedentary Behaviour and Physical Activity in Older Adults." PLoS One 2018.