Heavy Baryons: A Combined Large N_c and Heavy Quark Expansion for   Electroweak Currents
  The combined large N_c and heavy quark limit for baryons containing a single heavy quark is discussed. The combined large N_c and heavy quark expansion of the heavy quark bilinear operators is obtained. In the combined expansion the corrections proportional to m_N/m_Q are summed to all orders. In particular, the combined expansion can be used to determine semileptonic form factors of heavy baryons in the combined limit. 
Boris A. Gelman