Representations and BPS states of 10+2 superalgebra
  The 12d supersymmetry algebra is considered, and classification of BPS states for some canonical form of second-rank central charge is given. It is shown, that possible fractions of survived supersymmetry can be 1/16, 1/8, 3/16, 1/4, 5/16 and 1/2, the values 3/8, 7/16 cannot be achieved in this way. The consideration of a special case of non-zero sixth-rank tensor charge also is included. 
R. Manvelyan, A. Melikyan and R. Mkrtchyan