theorem Th39:
  for X1, X2, Y1, Y2 being non empty SubSpace of X st X1,Y1
  constitute_a_decomposition & X2,Y2 constitute_a_decomposition holds X1 misses
  X2 & Y1,Y2 are_weakly_separated implies X1,X2 are_separated
by Th37,TSEP_1:78;
