Dong HP, Holth A, Ruud MG, Emilsen E, Risberg B, Davidson B. Measurement of apoptosis in cytological specimens by flow cytometry: comparison of Annexin V, caspase cleavage and dUTP incorporation assays. Cytopathology. 2011 Dec;22(6):365–72. doi: 10.1111/j.1365-2303.2010.00811.x. PMID: 21054589.