The age deficit on photopic counterphase flicker: Contrast, spatial frequency, and luminance effects
Canadian Journal of Experimental Psychology/Revue canadienne de psychologie expérimentale (2002) - Comment
doi: 10.1037/h0087395  issn: 1878-7290  issn: 1196-1961  pubmed: 12271748 

Jody C. Culham, Donald W. Kline