Ludwig Reinhold Geissler, «The measurement of attention», The American Journal of Psychology (1909): 473–529; William A. Johnston, Steven P. Heinz, «Flexibility and capacity demands of attention», Journal of Experimental Psychology: General 107, № 4 (1978): 420; Robin A. Barr, «How do we focus our attention?», The American Journal of Psychology (1981): 591–603.
