The development and psychometric assessment of a questionnaire to assess sleep and daily troubles in parents of children and young adults with severe psychomotor impairment.
A.L. Tietze, B. Zernikow, M. Otto, G. Hirschfeld, E. Michel, M. Koh, M. Blankenburg, Sleep Medicine 15 (2014) 219–227.

Snake: the development and validation of a questionnaire on sleep disturbances in children with severe psychomotor impairment
M. Blankenburg, A.-L. Tietze, T. Hechler, G. Hirschfeld, E. Michel, M. Koh, B. Zernikow, Sleep Medicine 14 (2013) 339–351.