ciao,possono esserti utili:
BIENIAWSKI Z.T.(1973)-Engineering classification of rock masses.Trans.S.afr.Inst.Civ.Eng.,vol.15,n.12,Johannesburg
BIENIAWSKI Z.T.(1976)-Classification system is used to predict rock mass behavior.World Construction,London
BIENIAWSKI Z.T.-(1979)-The geomechanics Classif.in rock engineering applications.Int.Soc.Rock Mech. 4°Congress,vol.2,Montreux