The Nobel Prize in Physiology or Medicine 1958
George Beadle, Edward Tatum, Joshua Lederberg
George Wells Beadle
Edward Lawrie Tatum
The Nobel Prize in Physiology or Medicine 1958 was divided, one half jointly to George Wells Beadle and Edward Lawrie Tatum "for their discovery that genes act by regulating definite chemical events" and the other half to Joshua Lederberg "for his discoveries concerning genetic recombination and the organization of the genetic material of bacteria".
MLA style: "The Nobel Prize in Physiology or Medicine 1958". Nobelprize.org. 23 May 2013 http://www.nobelprize.org/nobel_prizes/medicine/laureates/1958/