Zunker, M., Althoff, H. K., Apel, J., Lässig, H. S., Schültke, L., & Schredl, M. (2015). Comparing questionnaire and diary measures for eliciting nightmare frequency. International Journal of Dream Research, 8(2), 129–134. https://doi.org/10.11588/ijodr.2015.2.23395