Holgado-Tello, F.P., Chachón-Moscoso, S., Barbero-García, I., & Vila-Abad, E. (2010). Polychoric versus Pearson Correlations in Exploratory and Confirmatory Factor Analysis of Ordinal Variables. Quality & Quantity: International Journal of Methodology, 44(1), 153-166. DOI: 10.1007/s11135-008-9190-y