Sorensen HT, Lash T, Rothman KJ. Beyond randomized controlled trials. A critical comparison of trials with non-randomized studies. Hepatology. 2006 Nov;44(5):1075-82. doi: 10.1002/hep.21404
Wood CE, Register TC, Franke AA, Anthony MS, Cline JM. Dietary soy isoflavones inhibit estrogen effects in the postmenopausal breast. Cancer Res. 2006 Jan 15;66(2):1241-9.