White Holes as the Asymptotic Limit of Evaporating Primordial Black   Holes
  This paper examines the interaction of an intense fermion field with all of the particle species of an attometer primordial black hole's (PBH)'s high energy Hawking radiation spectrum. By extrapolating to Planck-sized PBH's, it is shown that, although Planck-sized PBH's closely simulate the zero absorption requirement of white holes, the absorption probability is not truly zero, and therefore, thermodynamically, Planck-sized PBH's are not true white holes. 
Jeffrey S. Lee and Gerald B. Cleaver
physics.gen-ph