The distributivity numbers of of P(om) /fin and its square
  We show that in a model obtained by forcing with a countable support iteration of length omega_2 of Mathias forcing h(2), the distributivity number of r.o.(P(omega)/fin)^2, is omega_1 but h, the one of P(omega)/fin, is omega_2. 
Saharon Shelah, Otmar Spinas