[Cambridge histories online] Holt, P. M - The Cambridge history of Islam. 1.A_ The central Islamic lands from pre-Islamic times to the first world war 1A(1977, Cambridge University Press) - libgen.lc
As the adminis- tration became more complicated, the status o f the higher ranks o f the bureaucracy rose relative t o the rest o f society; and the distinction be- tween
thetribal
andlandowning classes on theonehand and the bureaucracy o n t h e other became less sharp.