Cropper ML, Haile M, Lampietti J, Poulos C, Whittington D. The demand for a malaria vaccine: evidence from Ethiopia. J Dev Econ. 2004 Oct 1;75(1):303-18.
Knox D, Gibson L, Zusman ME, Gallmeier C. Why college students end relationships. Coll Stud J. 1997 Jan 1;31(4):449-52.