from APS (American Physics Society):

The 2013 Physics Nobel Prize has been awarded to François‎ Englert (Universite Libre de Bruxelles) and Peter Higgs (University of Edinburgh) who were instrumental in developing the theory that helps explain the origin of mass of elementary particles and predicts the existence of the Higgs Boson. The landmark papers the Laureates published that laid the foundation for spontaneous symmetry breaking appeared in the flagship APS journal Physical Review Letters in 1964 and are freely available to the general public.

more info - including links to original 1964 papers.