Prakapenka AV, Hiroi R, Quihuis AM, Carson C, Patel S, Berns-Leone C, Fox C, Sirianni RW, Bimonte-Nelson HA. Contrasting effects of individual versus combined estrogen and progestogen regimens as working memory load increases in middle-aged ovariectomized rats: one plus one does not equal two. Neurobiol Aging. 2018 04; 64:1-14.