D-branes and Closed String Field Theory
  We construct solitonic states in the OSp invariant string field theory, which are BRST invariant in the leading order of regularization parameter. One can show that these solitonic states describe D-branes and ghost D-branes, by calculating the scattering amplitudes. 
Nobuyuki Ishibashi, Yutaka Baba, Koichi Murakami