Magnetization loop and critical current of porous Bi-based HTSC
  The magnetization of porous $Bi_{1.8}Pb_{0.3}Sr_2Ca_2Cu_3O_x$ have been investigated. The experimental magnetization hysteretic loops of $M(H)$ were described in the frames of Val'kov -- Khrustalev model developed for type II granular superconductors. 
D.M. Gokhfeld, D.A. Balaev, S.I Popkov, K.A. Shaykhutdinov, M.I.   Petrov