“…Cvetkovió (1986) (Vy'hitaker, 1969(Vy'hitaker, , 1986Bachmat and Bear, 1986). Using an order of magnitude analysis, Carbonell and Whitaker (1984) Whitaker, 1986;Hassanazdh and Gray, 1987 tensor, thus forming a quantity fol which a constitutive relation is for.med (e.g., Hassanizadeh and Glay, 1980;Shapiro, 1981). Alternatively, it can be tr.eated sepalately and a sepalate constitutive equation fot 1í-t¿tt¡ >/ can be assumed (e.g., Gray and O'Neill, 1976;Bear and Bachmat, 1986).…”