Liu SY, Trope GE, Buys YM, El-Defrawy SR, Khan AM, Jin YP. Visual impairment and the Ontario disability support program. Can J Ophthalmol. 2020 Jun;55(3):212-20. doi: 10.1016/j.jcjo.2019.12.009
Parsley (Edwards) TL. Review of the phantom respondents: opinion surveys and political representation. J Off Stat. 1994;10(3):351-5.