Warttig SL, Forshaw MJ, South J, White AK. New, normative, English-sample data for the Short Form Perceived Stress Scale (PSS-4). J Health Psychol. 2013 Dec;18(12):1617-28. doi: 10.1177/1359105313508346
Morant SV, Gnanasakthy A. A new approach to the mathematical formulation of lactation curves. Anim Prod Sci. 1989 Oct;49(2):151-62.