On dispersionless BKP hierarchy and its reductions
  Integrable dispersionless Kadomtsev-Petviashvili (KP) hierarchy of B type is considered. Addition formula for the $\tau$-function and conformally invariant equations for the dispersionless BKP (dBKP) hierarchy are derived. Symmetry constraints for the dBKP hierarchy are studied. 
L.V. Bogdanov and B.G. Konopelchenko