Wheatstone Bridge Circuit, Temperature Measurement?

Fig 1 shows a Wheatstone bridge used to measure the temperature. ume that dT, changes in temperature, with respect to dR, (Rtp=R+dR ) change in resistance of thermistor, is described by dT=k dR, where k is constant. Derive the relationship of Vout and dT. Discuss the effect of the variable resistance . (note : cannot manage to post the fig...pls email me for the fig, thanks)