Mr. grossel, i do know that this circuit works as a partial shmitt trigger. when the product of the open loop gain and β is large in a schmitt trigger, the output is not related to input in a linear manner, but instead shows two states of +Vss and -Vss. Also, the positive feedback gives a hysteresis. and when the differential input is< 0, the output remains at +Vss and when the capacitor here which replaces the external power supply in a schmitt trigger charges to β.Vss(voltage equal to that supplied in the positive terminal of the opamp), the differential output becomes 0 and the output shifts to - Vss. Hence, the capacitor's charging and discharging causesthe circuit's output to oscillate between + and - Vss and it behaves as an astable multivibrator. I hope i am right.