"Firstly, it must be said that conventional instrumentation is not adequate for flight in the vicinity of the stall; pitch attitude can be most misleading, airspeed and altitude and vertical speed are only component parts of the one parameter which is all important - incidence - and in isolation, and indeed in sensible combination, these individual parameters can be either misleading or nearly valueless. The only valuable parameter is incidence. This is what dictates the behaviour of the aeroplane and this is what needs to be presented to the pilot."
From: "Handling the Big Jets", page 124, D.P. Davies, Third Edition, Civil Aviation Authority, December 1971